Digibrid crossing. Examples of solutions of typical tasks. The main terms of genetics. Problem design scheme

The patterns of heredity, their cytological foundations. The patterns of inheritance established by the city of Mendel, their cytological foundations (mono- and digibrid crossing). T. Morgana laws: the adhesive inheritance of the signs, a violation of the clutch of genes. Genetics floor. Inheritance of signs lucked with floor. The interaction of genes. Genotype as holistic system. Human genetics. Methods for studying human genetics. Solution of genetic tasks. Drawing up crossing schemes

The patterns of heredity, their cytological foundations

According to the chromosomal theory of heredity, each pair of genes is localized in a pair of homologous chromosomes, and each chromosome carries only one of these factors. If you imagine that the genes are point objects on direct-chromosomes, then schematically homozygous individuals can be recorded as a || a or a || a, while heterozygous - a || a. In the formation of Heames in the process of Maiz, each of the genes of a pair of heterozygotes will be in one of the genital cells.

For example, if we crossed two heterozygous individuals, then, subject to the formation of each of them, only a pair of weights can obtain only four subsidiaries, three of which will carry at least one dominant gene A, and only one will be homozygoten on a recessive gene but, i.e. the patterns of heredity are statistical.

In those cases, if the genes are located in different chromosomes, then in the formation of heats the distribution between them alleles from this pair of homologous chromosomes occurs completely independently of the distribution of alleles from other pairs. It is the random arrangement of homologous chromosomes at an equator of spindle in metaphase I MEIOS and their subsequent discrepancy in Anafase I leads to a variety of recombinations of alleles in gates.

The number of possible combinations of alleles in male or female gates can be determined by the general formula 2 n, where n is the number of chromosomes characteristic of the haploid set. In humans, n \u003d 23, and the possible number of combinations is 2 23 \u003d 8388608. The subsequent combination of the heights in fertilization is also random, and therefore, in the offspring, an independent splitting for each pair of features can be fixed.

However, the number of signs of each organism many times more than the number of its chromosomes, which can be discharged under the microscope, therefore, each chromosome must contain many factors. If you imagine that some individuals, heterozygous in two pairs of genes located in homologous chromosomes, are formed by gear, it should be considered not only the likelihood of hamets with the initial chromosomes, but also hamets that have been changed as a result of a crosslinker in Proofase I of Maizo chromosome. Consequently, in the offspring there will be new combinations of signs. The data obtained in experiments on the drosophyl, formed the basis chromosomal theory of heredity.

Other fundamental confirmation of the cytological basis of heredity was obtained in the study various diseases. So, a person has one of the forms of cancer due to the loss of a small area of \u200b\u200bone of the chromosomes.

The patterns of inheritance established by the city of Mendel, their cytological foundations (mono- and digibrid crossing)

The main patterns of independent inheritance of signs were opened by G. Mendel, who achieved success, applying a new hybridological method in its research at that time.

The success of Mendel was ensured by the following factors:

• a successful choice of an object of study (pea sowing), which has a short vegetation period, is self-polished plant, gives a significant amount of seeds and is represented by a large amount of varieties with well-distinguishable features;
• using only pure pea lines, which for several generations did not give splitting signs in the offspring;
• concentration only on one or two signs;
• experiment planning and compilation of clear crossing schemes;
• accurate quantitative count of the received offspring.

For research, Mendel selected only seven signs that have alternative (contrast) manifestations. Already in the first crossings, he noted that in the offspring of the first generation when cropping plants with yellow and green seeds, all the offspring had yellow seeds. Similar results were obtained and in the study of other signs. Signs that prevailed in the first generation, Mendel called dominant. The same of them who were not manifested in the first generation were called recessive.

Individuals who gave splitting in the offspring were called heterozygous, and individuals who did not give splitting, - homozygous.

Signs of pea, the inheritance of which was studied by G. Mendel

Crossing, in which the manifestation of only one character is being studied, is called mono-librid. In this case, the patterns of inheritance of only two options for one feature, the development of which is due to a pair of allele genes. For example, a sign of the "color of a flower whisk" in pea has only two manifestations - red and white. All other signs inherent in these organisms are not taken into account and are not taken into account in the calculations.

Scheme of monohybrid crossing is as follows:

Crossed two pea plants, one of which had yellow seeds, and the other was green, in the first generation of Mendel received plants exclusively with yellow seeds, regardless of how the plant was chosen as a maternal, and what a paternal. The same results were obtained in crossings on other features, which gave the city of Mendel to formulate the law uniformity of the hybrids of the first generationwhich is also called first Law Mendel and dominance law.

First Law Mendel:

When crossing homozygous parental forms that differ in one pair of alternative features, all the hybrids of the first generation will be uniform both according to the genotype and the phenotype.

A - yellow seeds; but - Green seeds.

In self-polling (crossing) of the first generation hybrids, it turned out that 6022 seeds have a yellow color, and 2001 is green, which roughly corresponds to the 3: 1 ratio. The discovered pattern was called law of splitting, or second law Mendel.

Second law Mendel:

When crossing the first generation heterozygous hybrids in the offspring, the predominance of one of the signs in the ratio of 3: 1 is observed along the phenotype (1: 2: 1 in genotype).

However, according to the individual phenotype, it is not always possible to establish its genotype, because as homozygots on the dominant gene ( AA) and heterozygots ( AA) There will be a manifestation of the dominant gene in the phenotype. Therefore, for organisms with cross-fertilization use analyzing crossing - crossing, in which the body with an unknown genotype is crossped with homozygotum according to a recessive gene to verify the genotype. At the same time, homozygous individuals according to the dominant splitting gene in the offspring are not allowed, whereas in the offspring of heterozygous, an equal number of individuals with both dominant and recessive features are observed:

Based on the results of their own experiments, the city of Mendel suggested that hereditary factors in the formation of hybrids are not mixed, and are stored unchanged. Since the relationship between generations is carried out through the grounds, he made that in the process of their formation, only one factor from the pair falls into each gamets (i.e., genetically chistically), and in fertilization, the steam is restored. These assumptions were called the rules of purity Games.

The rule of purity Games:

With the games of the genes of one pair are divided, i.e., each gamet carries only one option of the gene.

However, organisms differ from each other in many signs, therefore, it is possible to establish the patterns of their inheritance only when analyzing two or more signs in the offspring.

Crossing in which the inheritance is considered and the accurate quantitative accounting of the offspring on two pairs of signs is called digibrid. If the manifestation of a larger number of hereditary signs is analyzed, then this is already polygibrid crossing.

Digibrid crossing scheme:

With a larger diversity, the definition of the genotypes of descendants becomes difficult, so for the analysis is widely used by the lattice of the Pennet, in which men's gamets are entered by horizontal, and vertically - women's. The genotypes of descendants are determined by the combination of genes in columns and lines.

For the dihybrid crossing of the city, Mentel chose two signs: seed painting (yellow and green) and their shape (smooth and wrinkled). In the first generation, the law of uniformity of the first generation hybrids was observed, and in the second generation there were 315 yellow smooth seeds, 108 - green smooth, 101 - yellow wrinkled and 32 green wrinkled. Counting showed that the splitting approached 9: 3: 3: 1, but for each of the signs, a ratio of 3: 1 (yellow - green, smooth - wrinkled) was preserved. This pattern was named the law of independent splitting of signs, or the third law of Mendel.

Third Mendel Law:

When crossing homozygous parental forms, differing in two or more pairs of signs, in the second generation there will be an independent splitting of these features in the ratio of 3: 1 (9: 3: 3: 1 with dihybrid crossing).

$ F_2 (9A_B_) ↙ (\\ Text "Yellow Smooth"): (3A_BB) ↙ (\\ Text "Yellow wrinkled"): (3aab_) ↙ (\\ Text "Green Smooth"): (1Aabb) ↙ (\\ Text "green wrinkled ") $

The third law of Mendel is applicable only to cases of independent inheritance when genes are located in different couples homologous chromosomes. In cases where the genes are located in a single pair of homologous chromosomes, the regularities of the clutch inheritance are valid. The patterns of independent inheritance of the signs established by G. Mendel are also often violated and in the interaction of genes.

T. Morgan laws: adhesive inheritance of signs, adhesion of genes

A new organism receives from parents not an axampy genes, but entire chromosomes, while the number of signs and, accordingly, determining their genes is much larger than chromosome. In accordance with the chromosomal theory of heredity, the genes located in the same chromosome are inherited. As a result, with dihybrid crossing, they do not give the expected splitting of 9: 3: 3: 1 and are not subject to the third law of Mendel. It would be possible to expect that the adhesion of genes is complete, and when the homozygous crossing of individuals and in the second generation, it gives the initial phenotypes in the ratio of 3: 1, and with the analyzing crossing of the first generation hybrids, the splitting should be 1: 1.

To verify this assumption, the American geneticist T. Morgan chose a couple of genes that control the body color (gray - black) and the shape of the wing (long - incharging), which are located in one pair of homologous chromosomes. Gray body and long wings are dominant signs. When crossing homozygous flies with gray body and long wings and homozygous flies with a black body and the embossed wings in the second generation, mostly parental phenotypes were obtained in the ratio close to 3: 1, but there was an insignificant number of individuals with new combinations of these signs. . These individuals are called recombinant.

However, conducting an analyzing crossing of the first generation hybrids with homozygotes for recessive genes, T. Morgan found that 41.5% of individuals had a gray body and long wings, 41.5% - black body and ridiculous wings, 8.5% - gray body And the inferior wings, and 8.5% - the black body and the inferior wings. He connected the resulting splitting with a crosslinker, which occurs in Profase I of MEIOS and proposed to be considered a distance between the genes in the chromosome of 1% crosslinker, subsequently called in his honor morganide.

The patterns of adhesive inheritance, established during the experiments on the drosophyl, were called t. Morgana.

Morgana Law:

The genes localized in the same chromosome occupy a certain location called locus, and inherited captured, and the clutch force is inversely proportional to the distance between the genes.

The genes located in the chromosome are directly at each other (the probability of crosslinker is extremely small), are called adhesive completely, and if there is still at least one gene between them, then they are not fully connected and their clutch is disturbed with crosslinic drive as a result of the exchange of areas of homologous chromosomes.

The adhesion phenomena of genes and cross trips make it possible to build maps of chromosomes with the order of genes caused by them. Chromosome genetic maps are created for many genetically well-studied facilities: drosophila, mice, man, corn, wheat, pea, etc. The study of genetic maps allows you to compare the structure of the genome from different species organisms what has important For genetics and selection, as well as evolutionary studies.

Genetics Paul

Floor - This is a combination of morphological and physiological features of the body providing sexual reproduction, the essence of which is reduced to fertilization, that is, the merger of male and female sex cells in the zygot, from which a new organism develops.

Signs for which one gear differs from the other is divided into primary and secondary. The primary sexual features include genitals, and all others are secondary.

A person has a secondary sexual signs are the type of physique, voice timbre, the predominance of muscle or adipose tissue, the presence of sobering on the face, cade, the mammary glands. So, in women, the pelvis is usually wider than shoulders, the adipose tissue prevails, the dairy glands are expressed, the voice is high. Men are different from them wider shoulders, the prevalence of muscle tissue, the presence of sobs on the face and caadon, as well as low voice. Humanity has long been interested in the question of why male and female individuals are born in the ratio of approximately 1: 1. The explanation of this was obtained when studying the karyotypes of insects. It turned out that the females of some bedbugs, grasshoppers and butterflies on one chromosome more than the males. In turn, males produce grounds that differ in the number of chromosomes, thereby determining the gender of the descendant. However, it was later found that most organisms have a number of chromosomes in males and females still does not differ, but one of the floors have a pair of chromosomes that do not fit each other in size, and the other all the chromosomes are paired.

In the karyotype of man also found a similar difference: men have two unpaired chromosomes. In the form of these chromosomes at the beginning of the division, the Latin letters X and Y are reminded, and therefore were named X- and Y-chromosomes. Men spermatozoa can carry one of these chromosomes and determine the floor of the future child. In this regard, the human chromosomes and many other organisms are divided into two groups: autosomes and heterochromosomes, or sex chromosomes.

TO autosomas attribute chromosomes are the same for both sexes, while sex chromosomes - These are chromosomes that differ from different floors and carrier information about sexual signs. In cases where the floor carries the same sex chromosomes, such as XX, they say that he gomozigoten., or homogamen (forms the same gametes). The other floor having different genital chromosomes (XY) is called gemezigot (not fully equivalent to allelic genes), or heterobamant. In humans, most mammals, flies of drosophila and other organisms are homogameteen female gender (XX), and the male - heterogamen (XY), while the birds are homogameteen a male floor (zz, or xx), and female - heterogamen (zw, or xy) .

The X chromosome is a large chromosome inequosome, which carries over 1500 genes, and many mutant alleles are caused by the development of severe hereditary diseases, such as hemophilia and daltonism. The Y-chromosome, on the contrary, is very small, it contains only about a dozen genes, including specific genes responsible for the development of male type.

The male karyotype is recorded as $ ♂ $ 46, XY, and the karyotype of women - as $ ♀ $ 46, XX.

Since gender chromosomes are produced in males with equal probability, the expected ratio of floors in the offspring is 1: 1, which coincides with the actual observed.

Bees differ from other organisms by the fact that the females develop from fertilized eggs, and males are from non-advocated. The ratio of the floors differs from the above, since the process of fertilization regulates the uterus, in the genital paths of which spermatozoa is reserved from spring for the whole year.

In a number of organisms, the floor can be determined in a different way: before fertilization or after it, depending on the conditions of the external environment.

Inheritance of signs lucked with floor

Since some genes are in sex chromosomes, unequal in representatives of opposite floors, the nature of the inheritance of signs encoded by genes is different from the total. This type of inheritance is called Chris Cross inheritance, since men inherit signs of the mother, and the women are the Father. Symptoms defined by genes that are in sex chromosomes are called seed with floor. Examples of signs captured with floorare recessive signs of hemophilia and daltonism, which are mainly manifested in men, since there are no allele genes in the Y-chromosome. Women are sick with such diseases only if both of the father and from the mother they received such signs.

For example, if the mother was hemophilia heterozygous carrier, then half of her sons, blood clotting will be broken:

X H - Normal blood coagulation

X h - non-blank blood (hemophilia)

Symptoms encoded in y-chromosome genes are transmitted purely by the male line and are called holyaric (The presence of a membrane between the fingers of the legs, the increased sophisticated sink edge).

The interaction of genes

Checking the patterns of independent inheritance at various facilities already at the beginning of the 20th century showed that, for example, in a night beauty when crossing plants with a red and white whites in the first-generation hybrids, the whites are painted in pink colorThen, in the second generation there are individuals with red, pink and white flowers in a 1: 2 ratio ratio. This brought researchers to the idea that allele genes can have a certain impact on each other. Subsequently, it was also established that both non-allele genes contribute to the manifestation of signs of other genes or suppress them. These observations became the basis of the presentation of genotype as a system of interacting genes. Currently, the interaction of allelic and non-allelegen genes is distinguished.

The interaction of allelic genes includes complete and incomplete dominance, codemination and overcompensation. Full dominance They consider all cases of interaction of allelic genes, in which a manifestation of an exclusively dominant sign is observed in a heterosigote, such as, for example, coloring and form of seed in pea.

Incomplete domination - This is the type of interaction of allelic genes, in which the manifestation of a recessive allele is more or less weakened by the manifestation of the dominant, as in the case of coloring the wretler of the night beauty (white + red \u003d pink) and wool in cattle.

Codominating This type of interaction of allelic genes is called, in which both alleles appear without weakening each other effects. A typical code of codomination is the inheritance of blood groups over the AB0 system.

As can be seen from the table, the I, II and III of the blood group are inherited by the type of complete dominance, while IV (AB) Group (genotype I A I B) is a case of coding.

Superclomination - this is a phenomenon in which in the heterozygous state dominant sign manifests itself much stronger than in homozygous; Supercilization is often used in selection and is considered to be Heterosisis - Hybrid power phenomena.

Special case of the interaction of allelic genes can be considered so-called flying geneswhich in a homozygous state lead to the death of the body most often in the embryonic period. The cause of the death of the offspring is the Pleiotropic effect of genes of gray color of wool in doodle sheep, platinum painting in foxes and lack of scales in mirrored carps. When crossing two heterozygous on these genes, the splitting on the studied attribution will be equal to 2: 1 due to the death of 1/4 of the offspring.

The main types of interaction of non-allelegen genes are complementarity, epistasis and polymeria. Complementation - This is the type of interaction of nonallerant genes, in which the presence of at least two dominant alleles of different steam is needed to manifest a certain state of the feature. For example, at pumpkin when crossing plants with spherical (AABB) and long (AABB) fruits in the first generation, plants appear with disk-forming fruits (AABB).

TO epistasis These phenomena of the interaction of nonallene genes include, at which one non-allest gene suppresses the development of a sign of another. For example, the chickens of the opament color is determined by one dominant gene, while the other dominant gene suppresses the development of color, with the result that most chickens have a white plumage.

Polymeria Call a phenomenon in which non-allele genes have the same effect on the development of a trait. Thus, quantitative signs are most often encoded. For example, human skin color is defined at least four pairs of nonallerant genes - the more dominant alleles in the genotype, the darker skin.

Genotype as a holistic system

The genotype is not a mechanical amount of genes, since the possibility of manifestation of the gene and the form of its manifestation depend on the conditions of the medium. In this case, the environment is understood not only the environment, but also the genotypic medium is other genes.

The manifestation of high-quality signs is rarely dependent on environmental conditions, although, if the mountain rolling has to drop the body of the body with white wool and apply a bubble with ice to it, then with time, black wool will grow in this place.

The development of quantitative features is much stronger dependent on environmental conditions. For example, if modern wheat varieties are cultivated without the use of mineral fertilizers, its yield will differ significantly from genetically programmed 100 and more centners with hectares.

Thus, only the "ability" of the organism is recorded in the genotype, but they only appear in cooperation with environmental conditions.

In addition, the genes interact with each other and, being in one genotype, can strongly affect the manifestation of the action of neighboring genes. Thus, for each individual gene, a genotypic medium exists. It is possible that the development of any sign is associated with the action of many genes. In addition, the dependence of several signs from one gene was revealed. For example, the oats in the color of floral scales and the length of their astest are determined by one genome. Drosophila gene is white color eye simultaneously affects the color of the body and internal organs, the length of the wings, a decrease in fertility and a decrease in life expectancy. It is possible that each gene is at the same time the main action gene for "its" feature and a modifier for other signs. Thus, the phenotype is the result of the interaction of the genes of the entire genotype with the environment in the Outogenesis of the individual.

In this regard, the well-known Russian geneticist M. E. Lobashev identified the genotype as The system of interacting genes. This holistic system has developed in the evolution process. organic WorldAt the same time, only those organisms were survived, in which the interaction of genes gave the most favorable reaction in ontogenesis.

Genetics of man

For a person as a biological species, the genetic patterns of heredity and variability established for plants and animals are fully fair. At the same time, the genetics of a person who studies the patterns of heredity and variability in a person at all levels of its organization and existence, occupies a special place among other sections of genetics.

The human genetics is simultaneously fundamental and applied science, since it has been studying the hereditary human diseases, which are currently described more than 4 thousand. It stimulates the development of modern areas of general and molecular genetics, molecular biology and clinical medicine. Depending on the problems of human genetics, it is divided into several directions developed into independent sciences: genetics normal signs Human, medical genetics, behavior and intelligence genetics, population human genetics. In this regard, in our time, a person as a genetic facility has been studied hardly better than the main model objects of genetics: Drosophila, Arabidopsis, etc.

The biosocial nature of a person imposes a significant imprint of research in the field of its genetics due to late puberty and large temporary gaps between generations, the smallness of the offspring, the impossibility of directed crossings for genetic analysis, the absence of clean lines, insufficient accuracy of registration of hereditary signs and small pedigrees, the impossibility of creating the same and strictly controlled conditions for the development of descendants from different marriages, relatively big number poorly differing chromosomes and the impossibility of experimental mutations.

Methods of studying human genetics

The methods used in human genetics are not fundamentally different from generally accepted for other objects - this genealogical, twin, cytogenetic, dermatoglyphic, molecular biological and population-statistical methods, method of hybridization of somatic cells and modeling method. Their use in human genetics takes into account the specifics of a person as a genetic facility.

Twin method It helps to determine the contribution of heredity and the influence of environmental conditions on the manifestation of a trait based on the analysis of the coincidence of these signs in single-person and diverse twins. So, most of one-time twins coincide the blood groups, the color of the eyes and hair, as well as a number of other signs, while the cow is sick at the same time both types of twins.

Dermatoglyphic method It is based on the study of individual features of the skin drawings of the fingers (dactyloscopy), palms and feet feet. Based on these features, it often makes it possible to identify hereditary diseases in a timely manificance, in particular chromosomal anomalies, such as Down Syndrome, Shereeshevsky - Turner, etc.

Genealogical method - This is the method of compiling a pedigree, with the help of which determine the nature of inheritance studied signs, including hereditary diseases, and predict the birth of descendants with appropriate features. He allowed me to reveal the hereditary nature of such diseases as hemophilia, daltonism, Huntington, etc., even before the opening of the main patterns of heredity. In the preparation of pedigrees, there are records of each of the family members and take into account the degree of kinship between them. Next, on the basis of the data obtained, a pedigree tree is built using a special symbolism.

The genealogical method can be used on one family, if there is information about a sufficient number of direct relatives of a person whose pedigree is drawn up - satua- on paternal and mother lines, otherwise collect information about several families in which this feature is manifested. The genealogical method allows you to install not only the inheritability of the sign, but also the nature of the inheritance: the dominant or recessive, autosomal or adhesive with the floor, etc. So, according to the portraits of the Austrian monarchs of the Habsburgs, the inheritance of the prenattention was established (strongly added to the lower lip) and "royal hemophilia" The descendants of the British Queen Victoria.

Solution of genetic tasks. Drawing up crossing schemes

All variety of genetic tasks can be reduced to three types:

1. Estimated tasks.
2. Tasks for determining the genotype.
3. Tasks for establishing the type of inheritance feature.

Feature settlement tasks It is the availability of information on the inheritance of the trait and phenotypes of parents, according to which the genotypes of parents are easy to install. They need to establish genotypes and phenotypes of offspring.

Task 1.What kind of color will have the seeds of the sorghum obtained as a result of crossing the clean lines of this plant with dark and bright coloring seeds, if it is known that dark color dominates the bright? What kind of color will have plant seeds derived from self-pollution of these hybrids?

Decision.

1. We denote genes:

A - Dark Seed Color, but - Bright seed painting.

2. We make a crossing scheme:

a) First, we write down the genotypes of parents, which, by the condition of the problem, are homozygous:

$ P (♀aa) ↙ (\\ Text "Dark Seeds") × (♂aa) ↙ (\\ Text "Bright Seeds") $

b) Then write the gametes in accordance with the rules of purity Games:

Gameti. BUT a.

c) Parly merge the gametes and write down the genotypes of descendants:

F 1 A. but

d) According to the law of dominance, all the first generation hybrids will have dark color, so we subscribe under the genotype of the phenotype.

Phenotype Dark seeds

3. Record the following crossing scheme:

Answer: In the first generation, all plants will have dark seed color, and in the second 3/4 plants there will be dark seeds, and 1/4 are bright.

Task 2. In rats, black wool color dominates the drone, and the normal length of the tail - above the shortened tail. How many descendants in the second generation from crossing homozygous rats with ferrous wool and a normal tail with homozygous rats with brown wool and a short tail had a black wool and a shortened tail, if 80 were born 80 rats?

Decision.

1. Record the condition of the problem:

A - black wool, but - brown wool;

In - normal tail length, B. - Cropped tail.

F 2 A_ bB. ?

2. Record crossing scheme:

Note. It should be remembered that the letter notation of genes is recorded in alphabetical orderwhile in genotypes cursive letter will always go before the line: a - before but, In - before b. etc.

From the lattice of the Pennet, it follows that the proportion of the black wool and a short-circuit tail was 3/16.

3. Calculate the number of rats with the specified phenotype in the offspring of the second generation:

80 × 3/16 × 15.

Answer: 15 Rousi had a black wool and a shortened tail.

IN tasks for the definition of genotype The nature of the inheritance of the feature is also given and the task is to determine the genotypes of offspring on the genotypes of the parents or vice versa.

Task 3. In the family, where the father had the III (c) group of blood according to the AB0 system, and the mother - ІІ (a) group, the child was born from І (0) by a group of blood. Determine the genotypes of parents.

Decision.

1. Remember the nature of the inheritance of blood groups:

Inheritance of blood groups on the AB0 system

2. Since it is possible for two variants of genotypes with II and III blood groups, the crossing scheme is written as follows:

3. From the above crossing scheme, we see that the child received from each of the parents recessive alleles I, therefore, parents were heterozygous on blood group genes.

4. We supplement the crossing scheme and verify our assumptions:

Thus, our assumptions were confirmed.

Answer: Parents are heterozygous by blood group genes: Mother's genotype - I A I, Father's genotype - I in I.

Task 4. Daltonism (color blindness) is inherited as a recessive sign with the floor. What children can be born from a man and women who normally distinguish colors, although their parents were a dalconic, and their mother and their relatives are healthy?

Decision.

1. We denote genes:

X D - normal color vision;

X D - Daltonism.

2. Install the genotypes of a man and a woman whose fathers were a rankon.

3. Record crossing scheme to determine possible genotypes of children:

Answer: All girls will have normal color vision (however, 1/2 girls will be carriers of Daltonism gene), 1/2 boys will be healthy, and 1/2 will be sick daltonism.

IN tasks for determining the nature of inheritance Only phenotypes of parents and offspring are given. Issues of such tasks are to find out the nature of the inheritance of the trait.

Task 5. From crossing chickens with short legs, 240 chickens were obtained, 161 of which were short-legged, and the rest were long-legged. How does this sign inherit?

Decision.

1. Determine the splitting in the offspring:

161: 79 $≈$ 2: 1.

Such splitting is characteristic of crosses in the case of deathal genes.

2. Since chickens with short legs were twice as long as long, let's say that this is a dominant sign, and it is this allele that the death effect is peculiar. Then the initial chickens were heterozygous. We denote genes:

C - short legs, with - long legs.

3. Record crossing scheme:

Our assumptions were confirmed.

Answer: The short-raziness dominates the long-beam, this allele is characterized by the fatal effect.

Genetics, its tasks. Heredity and variability - the properties of organisms. Major genetic concepts. Chromosomal theory heredity. Goty as a holistic system. Development of knowledge about genotype. Man genome.

The patterns of heredity, their cytological foundations. Mono- and Digibrid crossing. The patterns of inheritance established by the city of parade. The adhesive inheritance of the signs, a violation of the clutch of genes. The laws of T. Mamargan. Genetics floor. Inheritance of signs lucked with floor. The interaction of genes. Solution of genetic tasks. Drawing up crossing schemes.

Variability of signs in organisms: modification, mutational, combinative. Types of mutations and their causes. The value of variability in the life of organisms and in evolution. Reaction rate. The harmful effect of mutagens, alcohol, drugs, nicotine on the genetic device of the cell. Protection of the medium from pollution by mutagenami. Identification of sources of mutagens in environment (indirectly) and evaluating the possible consequences of their influence on its own body. Hereditary human diseases, their causes, prevention.

Selection, its tasks and practical importance. Doctrine N.I. Vavilov on the centers of the diversity and origin of cultivated plants. The law of homologous series in hereditary variability. Methods for eliminating new varieties of plants, rocks of animals, microorganisms strains. The value of genetics for selection. Biological basis growing cultivated plants and pets.

Biotechnology, cell and genetic engineering, cloning. The role of cell theory in the formation and development of biotechnology. The value of biotechnology for the development of breeding, agriculture, microbiological industry, conservation of the gene pool of the planet. Ethical aspects of the development of some studies in biotechnology (human cloning, directed changes in the genome).

In the previous article, we talked about the tasks of the C6 line as a whole. Starting from this post will be dealt with specific challenges in genetics, which were included in the test tasks of past years.

Have a good idea of \u200b\u200bsuch biological discipline as genetics - the science of heredity and variability is just necessary for life. Moreover, genetics in our country has such a long-suffering story ...

To think only, Russia from the leading country in the field of study of genetics at the beginning of the twentieth century turns into a dense monster on etching from the consciousness of people even simply genetic terminology since the late 30s to the mid-50s.

Is it possible to forgive the mode of killing torture and hunger of the greatest genetics, a noble servant to the people and science, the creator of the All-Union Institute of Crops in Leningrad, Academician (1887 - 1943) .

Let's start the analysis of the actual tasks of the C6 line with tasks on digibrid crossingrequiring knowledge According to the inheritance of the signs of two pairs of allele genes (but who are in relation to each other with nonallers), located in different vapors of homologous chromosomes, so inherited .

The most amazing thing is that the level of complexity of these tasks is very different , What are you with you now and make sure the examples of solving several tasks.

Studying the material of this article, thanks to my detailed explanations, I hope that more complex tasks for you will be understandable. And for a more successful development of tasks on a dihybrid crossing, I suggest your book:

Task 1. About pigs on dihybrid crossing (simplest)

In pigs, it is dominated by red, the long bristle (B) is dominated by a wool (a). The genes are not clips. What offspring can be obtained when crossing black with a long bristle digerozygous male with a homozygous black female with a short bristle. Make a problem solving scheme. Determine the genotypes of parents, offspring, phenotypes of offspring and their ratio.

First I want to draw your attention to such moments :

First, why is this task on a dihybrid crossing? The task requires to determine the distribution in the inheritance of two signs: wool coloring (a or a) and length (B or B). Moreover, it is indicated that the genes are adhered, that is, the studied signs are located in different pairs of homologous chromosomes and inherited from each other under the law of Mendel. This means that the offspring will be formed from all possible random combinations of Games formed by the male and female.

Secondly, it is this task for a dihybrid crossing is the simplest of this type of tasks. It stipulates in advance that the signs studied are not adaptable. In addition, melzu can (without analyzing all sorts of combinations of the birth of offspring) on \u200b\u200bthis phenotype of parents to record their genotype.

Decision:

1) parents genotypes :

male AAVB - Since about the male is told in the condition of the task, that it is digerozygoten, that is, heterosigoten on both studied signs, then in the record of its genotype for each sign present : A - dominant black wool color and a - recessive red wool color; B - dominant long bristle and B - recessive short;

female AABB. - Since it is said about it that she homocigarette in the color of wool, which is also black, it means that they write only AA, and about the length of the wool is not said homoit is valuable or goetherosigrate because this information would be superfluous !!!(and so it is clear that if the female wool is short, then it can also be only homocigo in this recessive Sign bB. ).

Sure, such long arguments about recording genotype parents on this in the condition of the task of them phenotypeyou do not need to give. The main thing is that you must first specify correctly In no case is not mistaken, the genotypes of both parents.

2) Gameti. :

digetero.zigo male will produce with equal probability four Surveying sperm AB, AB, AB, AB (According to the law of purity, Games, as a result, each gameta can have only one allele of any gene. And since the inheritance of two signs at once is being studied, then in each Games we enter one allelic genome of each studied sign);

digomociroby female (AABB.- How we found out this genotype ) will have everything the same egg cells - AB.

3) offspring :

since all same type of female eggs AB may be fertilized by any four types of spermatozoa AB, AB, AB and AB with equal probability, then the birth of descendants with such

four Genotypes : AAVB, AABB, AAVBand AABB. in relation to 1: 1: 1: 1 (25%, 25%, 25%, 25%)

and two Phenotypes : A-V- - Black long-haired - 50% and A-bb. - Black Shorthair - 50% (spaces are recorded by those places where absolutely no difference for manifestationsphenotype What is the second dominant or recessive gene in these pairs of allelic genes may be present ).

So, We fully answered questions : The decision was made according to the standard scheme (parents, gametes, offspring), the genotypes of parents and offspring were identified, the phenotypes of the offspring were determined and the possible ratio of genotypes and the phenotypes of offspring was determined.

Task 2. About the plant Durama on a dihybrid crossing, but with more complex Condition.

The plant is dura with purple flowers (a) and smooth boxes (b), crossed with a plant having purple flowers and spiny boxes. In the offspring, the following phenotypes were obtained: with purple flowers and spiny boxes, with purple flowers and smooth boxes, with white flowers and spiny boxes, with purple flowers and smooth boxes. Make a problem solving scheme. Determine the genotypes of parents, offspring and the possible ratio of phenotypes. Install the character inheritance character.

Note, that in this task we can no longer immediately definite answer the question about the genotype of parents, and therefore immediately Collect full information about gates They produced. It is possible to make only carefully analyzing the information about phenotypes offspring.

In response still have to not forget to specify character Inheritance of signs (independently inherited signs or adhesion). In the previous task it was given.

Decision:

1) We will define first albeit ambiguous Possible genotypes of parents

R: A - bb (PURP., Gladk.) And A - B - (PURP., Tarrow.)

2) Also during the ambiguous write information about the goves produced by them

G: AB, - B and AV, A -, - B, - -

3) We write on the basis of the well-known phenotype of the offspring their possible genotypes

F1 A - B - (PURP., Kolyuk.) A - BB (PURP., Gladk.)

...... AAAV - (White, Kolyuk.) AABB (white, smooth.)

Now, the most important information that we can extract from the foregoing:

a) Since among the offspring there are plants with smooth boxes (and this is a recessive sign), then genotypes both Parents before Must have gene b. That is, we can already enter the second parent genotype B. (small): A-in b;

b) Since among the offspring there are plants with white flowers (and this is a recessive sign), then genotypes both parents must have a gene but (small);

4) Only now we can completely write down the genotypes of both parents. : .. … ………………….. AABB. and AAAVB and produced by them ………………………………………….

gameti. : …. AB, AB and AB, AB, AB, AB

5) Since under the condition of the task in the offspring, all possible combinations of plant signs were discovered :

............ "With purple flowers and spiny boxes,

............ .. with purple flowers and smooth boxes,

............ .. with white flowers and spiny boxes,

............ .. with white flowers and smooth boxes, "

then it is possible only when independent inheritance signs;

6) Since we have determined that signs are not clips and inherited independently of each other, it is necessary to produce all possible combinations of crossings of the existing Games. It is convenient to record using the Pennet's grille. In our task, she will be, thank God, not a classic (4 x 4 \u003d 16), and only 2 x 4 \u003d 8 :

G. : AB AB AB

AB AABB AABB AABB AABB

............ .. Purp.Coluch Purp. Close-up Purp.Coluch Purp.Gladk

aU AABB AABB AABB AABB

............ PURP.CHUKH PURPE. CHALD BL

7) the distribution in the offspring will

by genotype:1 AAVB: 1 ABB: 2 AAVB: 2 AABB: 1 AAVB: 1 AABB

according to the phenotype: 3/8 - purple spiny (A-BB);

........................ 3/8 - Purple Smooth (A-BB);

.................................... 1/8 - White Bearing (AAVB);

........................ 1/8 - White Smooth (AABB).

Task 3. Very simple, if you understand in the sense of genetic terminology

From the crossing of 2 varieties of barley, one of which is a bark-tight cooler, and the other is a multidigious loose, obtained hybrids F 1, with a double-ripped rubber spray. What results on the phenotype and genotype will turn out in return crossings if the inheritance of the signs is independent? Make crossings schemes.

Because it is said that they crossed sort barley (yes, please, "appears" the word variety), it means that homozygous Organisms on both studied features. And what signs here are considered:

a) the form of the column and b) its quality. Yes, it is also said that the inheritance of signs is independent, then we can apply the calculations following the 3rd law of Mendel for the dihybrid crossing.

It is also said that hybrids in F 1 possessed. They were with a double-rich spacing - it means these signs and are dominant over the multi-roman and the density of the spike. Therefore, we can now introduce the designations of alleles of the genes of these two signs studied and will not be mistaken in the correctness of the use of large and small letters of the alphabet.

Denote:

alllel gene of a two-row chaser BUT, and multi-row - but;
Allel Rajle Chase Gene IN, and tight - b.,
Then the genotypes of the original two varieties of barley will look like this: AABB. and aabb.. From their crossing in F 1 it turns out hybrids: Aabb..

Well, now I have a return crossing of hybrids Aabb. With each of the initial parental forms separately with Aabb.and then with aabb., I am sure that it will not be difficult for anyone, is it not true?

Task 4. "Do not redhead, at all, not a redhead, do not redish, and golden"

Woman S. by brown eyes And red hair married a man with not red hair and blue eyes. It is known that the father of the woman's eyes were brown, and the mother had blue, both had red hair. Father men were not red hair and blue eyes, Mother - brown eyes and red hair. What are the genotypes of all these people? What could be the eyes and hair in children of these spouses?

Allel gene responsible for the manifestation of karelo eye color BUT (This is well known that the brown color of the eyes dominates blue color), and the allel blue eye gene, respectively, will but. Be sure to the same letter of the alphabet, as this is one sign - the color of the eyes.

Allel gene is not red hair (hair color - the second studied sign) we denote INSince he dominates the allele that is responsible for manifestation of red hair color - b.

The genotype of a woman with brown eyes and red hair we can only write out the incompleteness, and so A-bb.. But since it is said that her father was carbonous with red hair, that is, with the genotype A-bb., and her mother was blue-eyed and also with red hair ( aABB.), then the second woman allele when BUT Could be only butthat is, its genotype will be AABB..

The genotype of blue-eyed men with non-red hair you can first record so : AAB-. But since his mother had red hair, that is BB., then the second allel gene when IN The man could have only B.. So Orbraz, the genotype of a man will be recorded Aabb.. Gotypes of his parents: Father - aab-; mother - A-BB.

Children from marriage analyzed spouses AABB X aabb. (and gamets, respectively : AB, AB and AB, AB) will be with equilibrium genotypes Aabb, Aabb, Aabb, Aabb Or on the phenotype: carbonous not redhead, carbonous redhead, blue-eyed are not redhead, blue-eyed redheads in the ratio 1:1:1:1 .

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Yes, now you yourself see what an unequal complexity may be tasks. Unfair, yes unfairly, I reply, as the reheet of the ege on biology. I need good luck, yes you need good luck!

But you see that luck will be useful only for those who are actually "in the subject." Without knowing the laws of heredity of Gregor Mendel it is impossible to solve the first task, so the conclusion may be one : .

In the next article, the biology tutor on Skype will analyze the tasks on Inheritance that correctly solve even less students.

For those who want to understand well how to solve problems on genetics on a dihybrid crossing, I can offer your book: "

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Who will have questions about skype biology tutorPlease contact the comments. I have a blog you can purchase answers to all tests Options FIPI For all the years of exams and.

Having worked out these topics, you should be able to:

1. Give definition: gene, dominant sign; recessive sign; allele; homologous chromosomes; Mono-librid crossing, cross hinge, homozygous and heterozygous organism, independent distribution, complete and incomplete dominance, genotype, phenotype.
2. With the help of the Pennet lattice, illustrate crossing over one or two features and indicate which numerical relationships of genotypes and phenotypes should be expected in the offspring of these crossings.
3. Say out the rules of inheritance, splitting and independent distribution of signs, the opening of which was the contribution of Mendel to genetics.
4. Explain how mutations may affect the protein encoded by one or another genome.
5. Specify possible genotypes of people with blood groups A; IN; Av; ABOUT.
6. Create examples of polygenic signs.
7. Specify the chromosomal gender determination mechanism and the types of inheritance of the lips with the mammalian genes, use this information when solving tasks.
8. Explain what is the difference between the signs adopted with the floor and signs dependent on the floor; Create examples.
9. Explain how genetic human diseases are inherited as hemophilia, daltonism, sickle cell anemia.
10. Name the features of plant selection methods, animals.
11. Specify the main directions of biotechnology.
12. To be able to solve the simplest genetic tasks according to this algorithm:

    Algorithm Solving Tasks

    • Determine the dominant and recessive sign according to the results of crossing the first generation (F1) and the second (F2) (under the condition of the task). Enter alphabetic designations: A - dominant A - recessive.
    • Record the genotype of individuals with a recessive feature or individuals with a value-known in the condition of the Gotype and Gamet problem.
    • Write down the genotype of hybrids F1.
    • Make a diagram of the second crossing. Write down the Gamets of F1 hybrids into the foam lattice horizontally and vertically.
    • Write down the genotypes of offspring in the crossbar cells. Determine the ratio of phenotypes in F1.

Task design scheme.

Letter notation:
a) dominant sign _______________
b) recessive sign _______________

Gameti.

F1. (first generation genotype)

Grid Pennet.

The ratio of phenotypes in F2:_____________________________
Answer:_________________________

Examples of solving problems on monohybrid crossing.

A task. "In the family of Ivanov, two children: Karaglasaya daughter and blue-eyed son. Mom of these children is blue-eyed, but her parents had brown eyes. How is the eye of the eyes in a person inheritant? What are the genotypes of all family members?".

An attribute of eye color is controlled by one gene (under the condition). Mom of these children is blue-eyed, and her parents had brown eyes. This is possible only in Tomlush, if both parents were heterozygous, therefore, brown eyes dominate the blue. Thus, grandmother, grandfather, dad and daughter had genotype (AA), and Mom and Son - aa.

A task. "The rooster with a pink ridge is crossed with two hebles, which also have a pink comb. The first gave 14 chickens, everything with a pink-shaped ridge, and the second is 9 chickens, of which 7 with rose-like and 2 with a leaf-shaped ridge. Knove is a monogenous autosomal sign. What are the Gotypes of all three parents? "

Before determining the genotypes of parents, it is necessary to find out the nature of the inheritance of the form of the ridge of the ridge. When crossing the rooster with the second chicken, 2 chicken with a leaf ridge appeared. This is possible with the heterozygousness of the parents, therefore, it can be assumed that the rose-shaped crest in the chickens dominates the sheets. Thus, the genotypes of the rooster and the second chicken - AA.

When crossing the same rooster with the first chicken cleavage was not observed, therefore, the first chicken was homozygous - AA.

A task. "In the family of carbonous right-handed parents were born a variety of twins, one of which is the carbonous left-handers, and the other blue-eyed right-hander. What is the probability of birth next babysimilar to their parents? "

The birth of the carrage-eyed parents of the blue-eyed child testifies to the recessivity of the blue painting of the eyes, respectively, the birth of the right-handed parents of the left-handed child indicates the recessiveness of the best ownership of the left hand compared to the right. We introduce the markings of alleles: a - brown eyes, and - blue eyes, in - right-handed, in - Lefty. We define genotypes of parents and children:

A_VB - a phenotypic radical, which shows that this child with Left-handed with brown eyes. The genotype of this child can be AAVA, AAVR.

A further solution of this problem is carried out in the traditional way by building a Pennet's lattice.

Stressed 9 options for the descendants that we are interested. Total possible options 16, so the likelihood of the birth of a child, similar to their parents is 9/16.

Ivanova T.V., Kalina GS, Software A.N. "General Biology". Moscow, "Enlightenment", 2000

• Topic 10. "Mono-librid and digibrid crossing." §23-24 p. 63-67
• Theme 11. "Genetics of the floor." §28-29 p. 71-85
• Topic 12. "Mutational and modifying variability." §30-31 p. 85-90
• Topic 13. "Selection." §32-34 p. 90-97

The sixth building of the ege on biology is tasks. For people who are just starting to engage in biology or exam preparation in particular, they suggest horror. Very vain. It is worth only to figure out how everything will become simple and easy. 🙂

Refers to basic levelWhen you correctly, you can get 1 primary score.

To successfully perform this task, the following topics given in the codifier should be aware of:

Topics in the codifier on Job number 6

Genetics, its tasks. Heredity and variability - the properties of organisms. Methods of genetics. Main genetic concepts and symbolism. Chromosomal theory of heredity. Modern ideas about the gene and genome

The patterns of heredity, their cytological foundations. The patterns of inheritance established by the city of Mendel, their cytological foundations (mono- and digibrid crossing). T. Morgana laws: the adhesive inheritance of the signs, a violation of the clutch of genes. Genetics floor. Inheritance of signs lucked with floor. The interaction of genes. Goty as a holistic system. Human genetics. Methods for studying human genetics. Solution of genetic tasks. Drawing up crossing schemes.

"RUME EGE" divides the tasks into two large groups: mono-librid crossing and digibrid crossing.

Before solving tasks, we suggest a small dictionary of terms and concepts to understand what is required of us.

Theory for cropping tasks

Signs are divided into two types: recessive and dominant.

« Dominant sign suppresses recessive"- stable phrase. What does suppresses? This means that in choosing between the dominant and recessive sign, it will be manifested by the dominant. Anyway. The dominant feature is denoted by the capital letter, and the recessive is small. Everything is logical. In order for the offspring to show a recessive sign, it is necessary that the gene is carrying a recessive sign and from female, and from the male.

For clarity: imagine a sign, for example, the color of the kitten's wool. Let us have two events development options:

1. Black wool
2. White wool

Black wool dominates over white. In general, in tasks always indicate what dominates what is dominated, applicants are not obliged to know everything, especially from genetics.

Black wool will then be denoted by a capital letter. Most often, A, B, C and then alphabetically are used. White wool, respectively, a small letter.

A-black wool.

a- white wool.

If the combinations are obtained during the merges: AA, AA, AA, then this means that the wool in the descendants of the first generation will be black.

If, when merging Games, the AA combination will turn out, then the wool will be white.

About what gamets from parents will be told in the condition of the task.

Gameti., or sex cells - reproductive cells having a haploid (single) set of chromosomes and participating, in particular, in gender reproduction.

Zygote - diploid cell resulting from fertilization.

Heterozygot - two genes defining one sign - identical (AA or AA)

Gomosigot - two genes defining one sign - different (AA)

Digibrid crossing - Crossing the organisms that differ in two pairs of alternative features.

Mono-librid crossing - Crossing, in which the crossed organisms differ only with one sign.

Analyzing crossing - crossing a hybrid individual with a person homozygous for recessive alleles.

Gregor Mendel - "Father" Genetics

So, how to distinguish these types of crossing:

With mono-librid crossing, we are talking about one sign: color, size, shape.

With dihybrid crossing, we are talking about a pair of signs.

With the analyzing crossing, one individual can be completely any, but the other gamete must be exclusively recessive signs.

Alleli. - various forms of the same gene located in the same areas of homologous chromosomes.

It sounds not very clear. Tell:

1 gene carries 1 sign.

1 Allel carries one character value (it can be dominant or recessive).

Genotype - A combination of genes of this body.

Phenotype- A combination of the characteristics inherent in the individual at a certain stage of development.

In tasks, they are often asked to specify the percentage of individuals with a specific genotype or phenotype or indicate the splitting of genotype or phenotype. If you simplify the definition of a phenotype, then the phenotype is an external manifestation of signs from the genotype.

In addition to all sorts of concepts, you need to know the laws of Gregor Mendel - Father Genetics.

Gregor Mendel crossed peas with fruits, characterized by the color and smoothness of the peel. Thanks to his observations, three laws of genetics appeared:

I. The law of uniformity of the hybrids of the first generation:

In the mono-librid crossing of different homozygotes, all descendants of the first generation will be the same through the phenotype.

II. Law of splitting

When crossing the descendants of the first generation, a splitting of 3: 1 is observed along the phenotype and 1: 2: 1 by genotype.

III. The law of independent splitting

With a dihybrid crossing of two different homozygotes in the second generation, a splitting of phenotype is observed in a ratio of 9: 3: 3: 1.

When the solution of the genetic tasks will be received, the question may be obtained: why should I know the laws of Mendel if I can still solve the task and find splitting in private events? Caution Answer: In some tasks, it may be necessary to specify the splitting on what law, but it is more likely to tasks with a detailed answer.

Arriving in theory, you can finally go to the tasks. 😉

Analysis of typical tasks number 6 of biology

Types of Games from Oracle

How many types of weights are formed in individuals with the AABB genotype?

We have two pairs of allelic chromosomes:

First pair: aa

Second steam: bb

These are all homozygotes. You can make only one combination: AB.

Types Games when crossing

How many types of weights are formed in digerozygous pea plants with dihybrid crossing (genes do not form a clutch group)? In response, write down the number.

Since the plants are digerozygous, then this means that on both of them they have one allele dominant, and the second-recessive.

We obtain AABB and AABB genotypes.

Gamets in tasks are denoted by the letter G, moreover without commas, in circles, they first indicate the grounds of one individual, then the point of the comma is set (;), they are written in the other individuals, also in circles.

Crossing is indicated by the "x" icon.

We drink gametes, for this we will move all the combinations:

Gamets at the first and second individuals turned out the same, so the genotype was the same. So we managed to 4 of different types Games:

Counting the share of digeterosigot

When crossing individuals with AAVB genotypes with aAVB (genes are not linked), the share (%) of heterozygotes on both alleles (digeterosigot) in the offspring will be ....

Let's make a lattice of Pennet. For it, we will write down the gamets of one individual in the column, the gametes of the other - in the string, we get the table:

We find diagerosigots in the table:

Total zygot: 16

DiGeterosigot: 4.

Calculate the percentage: \u003d

Application of Mendel laws

The rule of the first generation uniformity will manifest itself if the genotype of one of the parents is AABB, and the other -

According to the rule of uniformity, monohybrid homozygotes must be crossed, one with a dominant sign, and the second one with recessive. So, the genotype of another individual must be AABB.

Answer: AAVR.

The ratio of phenotypes

The genotype of one of the parents will be AABB if with an analyzing dihybrid crossing and independent inheritance of signs there is a splitting along the phenotype in offspring in the ratio. The answer is recorded in the form of a sequence of numbers showing the ratio of the resulting phenotypes, in order of their decrease.

Analyzing dihybrid crossing, which means that the second individual is recessive Digomosigot: AABB.

Here you can do without a lattice of Pennet.

Generations are denoted by the letter F.

F1: AABB; Aabb; aabb; Aabb.

All four options for phenotypes are different, so they belong to each other as 1: 1: 1: 1.

Answer: 1111.

The ratio of genotypes

What is the ratio of genotypes in the offspring, obtained from the crossing of individuals with the AAVB x AVA genotypes?

AAVB X AAVA

F1: AABB; Aabb; aabb; Aabb.

All 4 genotypes are different.

Inheritance of certain signs or diseases

What is the likelihood of the birth of healthy boys in the family, where the mother is healthy, and the father is sick with hypertrichoz - a disease due to the presence of a gene linked with Y-chromosome?

If the sign is confused with the Y-chromosome, it means that it does not affect the X-chromosome.

Female Paul Gomosigoten: XX, and Male-Heterosigot Hy.

Solving tasks with sex chromosomes is practically no different from solving tasks with autosomas.

We will make a sign of the gene and the sign that should also be for and for tasks about autosomal chromosomes, if signs are indicated and this is important.

The letter over Y denotes that the gene with this chromosome is connected. Signs are dominant and recessive, they are denoted by capital and small letters, they can relate both to the C chromosome and the Y-chromosome depends on the task.

♀ХХ x xy a

F1: Hx Girl, Healthy

Xy a - boy, sick

Boys born in this pair will be 100% sick, means 0% healthy.

Groups of blood

What group of blood via the avo system has a man with genotype I b i 0? In response, write down the number.

We use the sign:

In our genotype, agglutinogens are recorded in and 0. This pair gives the third group of blood.

Work with a scheme

According to the pedigree depicted in the figure, determine the probability (as a percentage) of the birth of parents 1 and 2 children with a sign indicated by black color, with full dominance of this feature. Answer write in the form of a number.

So, learn to analyze similar schemes.

We see that the sign is manifested in both men and women, it means that it is not adhesive with the floor.

It is manifested in each generation, which means that dominant.

Since one of the children has a couple, a sign manifested itself, which means parents-heterozygotes.

F1: A- manifests

A- manifests

A- manifests

aa - not manifest

3 - manifests itself from 4