Interaction of non-allelic genes. Interaction of non-allelic genes: types and forms The types of interaction of allelic genes include

With the accumulation of scientific experience, contradictions appeared with Mendel's third law of independent inheritance. The offspring were divided by phenotype in a ratio of 15:1 or 9:7, and not 9:16 according to Mendel. This indicates a certain relationship of non-allelic genes.

Mechanism

Non-allelic genes are located in different parts of the chromosomes and encode different types of proteins. Genes do not directly affect each other, so the interaction occurs in the cytoplasm at the level of proteins that are encoded by certain genes.

Rice. 1. Non-allelic genes.

The interaction mechanism can proceed according to one of three scenarios:

• simultaneous action of two enzymes that encode two non-allelic genes;
• one non-allelic gene forms a protein that affects the work of another non-allelic gene (suppresses or activates);
• two proteins encoded by two non-allelic genes act on the same process, enhancing or restoring the same trait.

One gene may be responsible for several phenotypic traits, or several genes may be responsible for one trait.

Kinds

There are several types of interaction of non-allelic genes, the main of which are described in detail in the table.

Rice. 2. Complementarity.

View	Description	Example
	A trait caused by two different genes appears only when two dominant alleles are combined. Such genes are called complementary. A trait is not formed in the absence of one gene. Segregation of phenotypic traits in F2 occurs in the ratio 9:7, 9:6:1, 9:3:4	A cross between sweet peas and white flowers. In F1, all offspring have purple flowers, because. a combination of dominant genes A and B encode an anthocyanin, giving a purple color. Individual genes do not form purple. Splitting occurs in F2 - 9 magenta (AB), 7 white (3 - Abb, 3 - aaB, 1 - aabb)
	One pair of genes suppresses the other, preventing the phenotypic trait from manifesting itself. The suppressing gene is called epistatic (suppressor or inhibitor gene), the suppressed is called hypostatic. The inhibitor is designated by the letter I, i. Epistasis can be dominant - suppression by the dominant gene (I>B, b) and recessive - suppression by the recessive gene (i>B, b). With dominance, gene splitting occurs in the ratio 7:6:3, 12:3:1, 13:3, with recessive manifestation - 9:3:4, 9:7, 13:3	Coloring of oat grain: A - black, B - gray. In F1, all grains will be black if gene A is epistatic (AaBB or IiBB). In F2, there will be a splitting according to the color of the grain - 12 black, 3 gray and 1 white. In 12 plants, the I-gene is necessarily present, in 3 it will be in a recessive state - i. One plant will get the iibb genes (no black and gray), so it will be white
Polymerism	Quantitative or dimensional traits that cannot be clearly separated by phenotype (height, amount of milk, fat content of livestock) are determined by a combination of genes. There are cumulative and non-cumulative types. In the first case, the manifestation of a trait depends on the sum of the actions of the genes (the more dominant genes, the brighter the trait). In the second case, the trait manifests itself with a dominant gene, the number of genes does not affect the manifestation of the phenotype. With a cumulative form in F2, splitting is observed in a ratio of 1:4:6:4:1, with a non-cumulative - 15:1. Polymer genes are designated with a single letter (A, a, B, b, etc.), and alleles with a number. For example, A1a1A2a2	The color of the human skin depends on the action of four genes: A1A1A2A2 - black color, A1A1A2A2 - White, A1A1A2A2, A1A1A2A2, A1A2A2A2A2, A1A1A2A2, A1A1A2A2, A1A1A2A2 - interim values ​​from the dark (almost black) to Svetlia (almost black) nod) shade

Rice. 3. Epistasis.

The multiple action of genes is called pleiotropy. The action of one gene, as a rule, is due to interaction with other genes. Most genes have this effect, so the genotype is a system of interacting genes.

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What have we learned?

Learned briefly about the types of interaction of non-allelic genes. There are three types of interaction - complementarity, epistasis, polymerization. For a trait to be complementary, two dominant genes must be present. Epistasis is characterized by suppression of the action of the second gene by one gene. Polymeria - the interaction of a set of genes. The interaction of many genes is called pleiotropy.

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The transmission of traits from generation to generation is due to the interaction between different genes. What is a gene, and what are the types of interaction between them?

What is a gene?

Under the genome at the present time, they mean the unit of transmission of hereditary information. Genes are located in DNA and form its structural sections. Each gene is responsible for the synthesis of a specific protein molecule, which determines the manifestation of a particular trait in humans.

Each gene has several subspecies or alleles, which cause a variety of traits (for example, brown eyes are due to the dominant allele of the gene, while blue is a recessive trait). Alleles are located in the same areas and the transmission of one or another chromosome causes the manifestation of one or another trait.

All genes interact with each other. There are several types of their interaction - allelic and non-allelic. Accordingly, the interaction of allelic and non-allelic genes is distinguished. How do they differ from each other and how do they manifest themselves?

Discovery history

Before the types of interaction of non-allelic genes were discovered, it was generally accepted that it was possible only (if there is a dominant gene, then the trait will appear; if it is not there, then there will be no trait). The doctrine of allelic interaction, which for a long time was the main tenet of genetics, prevailed. Dominance has been carefully studied, and such types of dominance as complete and incomplete dominance, co-dominance and overdominance have been discovered.

All these principles obeyed the first one, which stated the uniformity of hybrids of the first generation.

Upon further observation and study, it was noticed that not all signs were adjusted to the theory of dominance. With a deeper study, it was proved that not only the same genes affect the manifestation of a trait or group of properties. Thus, forms of interaction of non-allelic genes were discovered.

Reactions between genes

As has been said, for a long time the doctrine of dominant inheritance prevailed. In this case, an allelic interaction took place, in which the trait manifested itself only in the heterozygous state. After various forms of interaction of non-allelic genes were discovered, scientists were able to explain hitherto unexplained types of inheritance and get answers to many questions.

It was found that gene regulation directly depended on enzymes. These enzymes allowed genes to react differently. At the same time, the interaction of allelic and non-allelic genes proceeded according to the same principles and patterns. This led to the conclusion that inheritance does not depend on the conditions in which genes interact, and the reason for the atypical transmission of traits lies in the genes themselves.

Non-allelic interaction is unique, which makes it possible to obtain new combinations of traits that determine a new degree of survival and development of organisms.

Non-allelic genes

Non-allelic genes are those genes that are localized in different parts of non-homologous chromosomes. They have one synthesis function, but they encode the formation of various proteins that cause different signs. Such genes, reacting with each other, can cause the development of traits in several combinations:

• One trait will be due to the interaction of several genes that are completely different in structure.
• Several traits will depend on one gene.

Reactions between these genes are somewhat more complicated than with allelic interaction. However, each of these types of reactions has its own features and characteristics.

What are the types of interaction of non-allelic genes?

• Epistasis.
• Polymerism.
• Complementarity.
• The action of modifier genes.
• Pleiotropic interaction.

Each of these types of interaction has its own unique properties and manifests itself in its own way.

It is necessary to dwell in more detail on each of them.

epistasis

This interaction of non-allelic genes - epistasis - is observed when one gene suppresses the activity of another (the suppressing gene is called an epistatic, and the suppressed gene is called a hypostatic gene).

The reaction between these genes can be dominant or recessive. Dominant epistasis is observed when the epistatic gene (usually denoted by the letter I, if it does not have an external, phenotypic manifestation) suppresses the hypostatic gene (it is usually denoted B or b). Recessive epistasis occurs when the recessive allele of the epistatic gene inhibits the expression of any of the alleles of the hypostatic gene.

Splitting according to the phenotypic trait, with each of these types of interactions, is also different. With dominant epistasis, the following picture is more often observed: in the second generation, according to phenotypes, the division will be as follows - 13:3, 7:6:3 or 12:3:1. It all depends on which genes converge.

With recessive epistasis, the division is: 9:3:4, 9:7, 13:3.

complementarity

The interaction of non-allelic genes, in which, when the dominant alleles of several traits are combined, a new, hitherto unseen phenotype is formed, and is called complementarity.

For example, this type of reaction between genes is most common in plants (especially pumpkins).

If the plant genotype has a dominant allele A or B, then the vegetable gets a spherical shape. If the genotype is recessive, then the shape of the fetus is usually elongated.

If there are two dominant alleles (A and B) in the genotype at the same time, the pumpkin becomes disc-shaped. If you continue to cross (i.e. continue this interaction of non-allelic genes with pumpkins of a pure line), then in the second generation you can get 9 individuals with a disc-shaped shape, 6 with a spherical shape and one elongated pumpkin.

Such crossbreeding makes it possible to obtain new, hybrid forms of plants with unique properties.

In humans, this type of interaction determines the normal development of hearing (one gene - the development of the cochlea, the other - the auditory nerve), and in the presence of only one dominant trait, deafness appears.

Polymerism

Often, the manifestation of a trait is based not on the presence of a dominant or recessive allele of a gene, but on their number. The interaction of non-allelic genes - polymerism - is an example of such a manifestation.

The polymeric action of genes can occur with or without cumulative action. During cumulation, the degree of manifestation of a trait depends on the overall gene interaction (the more genes, the more pronounced the trait). The offspring with a similar effect is divided as follows - 1: 4: 6: 4: 1 (the degree of expression of the trait decreases, that is, in one individual the trait is maximally pronounced, in others its extinction is observed up to complete disappearance).

If no cumulative action is observed, then the manifestation of the trait depends on the dominant alleles. If there is at least one such allele, the trait will take place. With a similar effect, splitting in the offspring proceeds in a ratio of 15:1.

Action of modifier genes

The interaction of non-allelic genes, controlled by the action of modifiers, is relatively rare. An example of such an interaction is as follows:

Such an interaction of non-allelic genes in humans is quite rare.

Pleiotropy

With this type of interaction, one gene regulates the expression or affects the degree of expression of another gene.

In animals, pleiotropy manifested itself as follows:

• In mice, dwarfism is an example of pleiotropy. It was noticed that when crossing phenotypically normal mice in the first generation, all mice were dwarfed. It was concluded that dwarfism is caused by a recessive gene. Recessive homozygotes stopped growing, their internal organs and glands were underdeveloped. This dwarfism gene influenced the development of the pituitary gland in mice, which led to a decrease in hormone synthesis and caused all the consequences.
• Platinum coloration in foxes. Pleiotropy in this case was manifested by a lethal gene, which, when a dominant homozygote was formed, caused the death of embryos.
• In humans, the pleiotropic interaction is illustrated by the example of phenylketonuria, as well as

The role of non-allelic interaction

In evolutionary terms, all the above types of interaction of non-allelic genes play an important role. New gene combinations cause the appearance of new features and properties of living organisms. In some cases, these signs contribute to the survival of the organism, in others, on the contrary, they cause the death of those individuals that will stand out significantly among their species.

Non-allelic interaction of genes is widely used in breeding genetics. Some species of living organisms are preserved due to such gene recombination. Other species acquire properties that are highly valued in the modern world (for example, breeding a new breed of animal with greater endurance and physical strength than its parent individuals).

Work is underway on the use of these types of inheritance in humans in order to exclude negative traits from and create a new, defect-free genotype.

Task number 1

Topic 22. Interaction of allelic and non-allelic genes

Questions of self-control

1. When do the laws of genetics formulated by G. Mendel work?

2. In what case does the law of adhesion apply?

3. Who formulated the law of adhesion?

4. Is linkage between genes absolute?

5. What are the main provisions of the chromosome theory

6. What is the meaning of the chromosome theory

1. Read the study material below.

2. Analyze tables from the application

3. Answer the self-control questions.

Genotype is a system of interacting genes. Both allelic and non-allelic genes located in different loci of the same and different chromosomes interact with each other.

Allelic genes enter into relationships of the type of dominance - recessiveness; There are complete and incomplete dominance, codominance, overdominance, multiple alleles.

Complete dominance- the dominant allele completely hides the presence of the recessive one.

incomplete dominance there is an intermediate sign.

Codominance- manifestation in heterozygotes of traits determined by two alleles.

For example, this is how blood groups are inherited in humans (each allele encodes a specific protein, and both are synthesized in heterozygotes.

overdominance- the dominant gene in the heterozygous state has a stronger expression than in the homozygous state. For example, a recessive lethal mutation is known in Drosophila, heterozygotes are more viable than homozygotes.

Multiple alleles, sometimes not two, but more genes may be among the alleles. In addition to the main - dominant and recessive - genes, intermediate ones appear, which behave as recessive in relation to the dominant, and as dominant in relation to the recessive.

Types of interaction.

1. Cooperation

2.Complementarity

3. Epistasis

4.Polymeria

5.Multiple action (pleiotropy)

Cooperation- the appearance of neoplasms under the joint action of two dominant non-allelic genes, when in a homozygous or heterozygous state a new trait develops that is absent in parental forms.

complementarity- a type of inheritance in which non-allelic genes complement each other.

Example :

When crossing yellow budgerigars with blue individuals, all first-generation hybrids are green. When these green hybrids are crossed with each other, splitting is observed in their offspring - 9 parts are green: 3 parts are yellow: parts are 3 parts are blue; 1 are often white.

Explanation.

Parental individuals were homozygous since all hybrids of the first generation are uniform. The appearance of a new variant of the trait (green color) in the first generation cannot be explained by incomplete dominance (because there are white individuals in the second generation).

It can be assumed that in budgerigars the presence of yellow pigment is determined by the dominant allele A, and the presence of blue pigment is determined by the dominant allele B. If the hybrids of the first generation have dominant alleles A and B, both yellow and blue pigments are synthesized, which together give a green color. In the absence of dominant alleles, some of the second generation hybrids have neither yellow nor blue pigments, and the plumage becomes colorless - white.

P: ♀АааВВ x ♂ааВВ

yellow blue

F 1: ♀АаВв x ♂АаВв

green green

F 2: 9A-B-: 3A - cc: 3aaB-: 1aavb

green yellow blue white

epitasis- a type of inheritance in which the action of one gene is suppressed by the action of another non-allelic gene.

For example, consider the inheritance of coat color in rabbits.

Dominant gene C - provides the synthesis of black pigment.

Recessive gene c - does not form a pigment.

There is another pair of alleles (A-a) that affects the distribution of the pigment, if already present.

Dominant gene A - causes an uneven distribution of pigment along the length of the hair pigment (accumulates at its base, while the tip of the hair is devoid of pigment (gray rabbits). Recessive gene (a) does not affect the distribution of pigment.

P: ♀CCAA x ♂CCaa

gray white

F 1 ♀СсАа x ♂ СсАа

gray gray

Deviation from Mendel's laws is caused by various types of gene interaction (with the exception of complete dominance), due to the genomic level of organization of hereditary material.

There are interactions of allelic and non-allelic genes.

The interaction of genes of one allele is called intraallelic. The following types of it are distinguished: complete dominance, incomplete dominance, overdominance, coding and allelic exclusion.

The interaction of genes of different alleles is called interallelic. There are the following types of it: complementarity, epistasis, polymerization and "position effect".

At complementarity the presence in one genotype of two dominant (recessive) genes from different allelic pairs leads to the emergence of a new variant of the trait. There are three types of complementary gene interaction.

I. Two dominant non-allelic genes separately do not have a phenotypic manifestation, but complementing each other, they determine a new variant of the trait.

The development of hearing in humans. For normal hearing, the human genotype must contain dominant genes from different allelic pairs - D and E. The D gene is responsible for the normal development of the cochlea, and the E gene is responsible for the normal development of the auditory nerve (DdEe). In recessive homozygotes dd the snail will be underdeveloped, and with the genotype her- auditory nerve. People with genotypes D-ee, ddE- and ddee will be deaf.

In mammals and humans, a specific protein is produced to protect against viruses. interferon. Its synthesis in the human body is due to the complementary interaction of two non-allelic genes located in different ( second and fifth) chromosomes.

Human hemoglobin contains 4 polypeptide chains, each of which is encoded by a separate independent gene. Therefore, 4 complementary genes are involved in the synthesis of hemoglobin.

II. One of the dominant complementary genes has a phenotypic expression, and the second does not; their simultaneous presence in the genotype determines a new variant of the trait. So in mice, the agouti coat color is inherited (at the base and at the end of the hair there is a black pigment, and in the middle part there is a yellow ring). Gene A determines the synthesis of black pigment, its allele a does not provide information for the synthesis of the pigment. Gene IN distributes the pigment along the hair unevenly, and its allele b- evenly:

Splitting - in the ratio 9:3:4.

III. Each of the complementary genes has its own phenotypic expression; their simultaneous presence in the genotype determines the development of a new variant of the trait. This is how the shape of the comb is inherited in chickens:

Splitting - in the ratio 9:3:3:1.

At epistasis a dominant (recessive) gene from one allelic pair suppresses the action of a dominant (recessive) gene from another allelic pair. This phenomenon is the opposite of complementarity. The suppressor gene is called suppressor (inhibitor) . Distinguish between dominant and recessive epistasis. An example dominant epistasis can serve polydactyly. Sometimes occurs in "perfectly healthy" parents. It is assumed that the effect of this allele in parents was suppressed by other genemi.

An example recessive epistasis is the "Bombay Phenomenon". In a woman who received the allele I B from her mother, 1 (0) blood group was determined phenotypically. In a detailed study, it was found that the action of gene I B (synthesis of antigen B in erythrocytes) was suppressed by a rare recessive gene, which in the homozygous state had an epistatic effect. In the manifestation of some hereditary metabolic diseases (fermentopathies), the main role is played by the epistatic interaction of genes, when the presence or absence of the products of one gene impedes the formation of active enzymes encoded by another gene.

At polymers genes from different allelic pairs affect the degree of manifestation of the same trait. Polymeric genes are usually denoted by a single letter of the Latin alphabet with numerical indices, for example, A 1 A 1 A 2 a 3 a 3, etc. Traits determined by polymeric genes are called polygenic(multifactorial). Thus, many quantitative and some qualitative traits are inherited in animals and humans: height, body weight, blood pressure, skin color, etc. The degree of manifestation of these traits depends on the number of dominant genes in the genotype (the more there are, the more pronounced the trait) and largely on the influence of environmental conditions. A person may have a predisposition to various diseases: hypertension, obesity, diabetes mellitus, schizophrenia, etc. These signs, under favorable environmental conditions, may not appear or be mild. This distinguishes polygenic inherited traits from monogenic ones. By changing environmental conditions and taking preventive measures, it is possible to significantly reduce the frequency and severity of some multifactorial diseases. The summation of "doses" of polymeric genes ( additive action) and the influence of the environment ensure the existence of continuous series of quantitative changes. Human skin pigmentation is determined by five or six polymeric genes. Dominant alleles predominate among the indigenous people of Africa, while recessive alleles predominate among representatives of the Caucasoid race. Mulattos are heterozygous and have intermediate pigmentation. Mulatto parents have both white and black children. The minimum number of polymeric genes at which a trait is expressed is called threshold effect.

Under "position effect" understand the mutual influence of genes of different alleles occupying nearby loci of the same chromosome. It manifests itself in a change in their functional activity. The Rhesus belonging of a person is determined by three genes located in the short arm of the first chromosome at a close distance from each other (closely linked). Each of them has a dominant and a recessive allele ( WITH, D, E and c, d, e). Organisms with a set of genes CDE/cDe And CDe/cDE genetically identical (they have the same overall balance of genes). However, in individuals with the first combination of genes, a lot of antigen is formed E and little antigen WITH, and in individuals with the second combination of alleles, on the contrary, there is little antigen E and a lot of antigen WITH. Probably, the close proximity of the E allele to the C allele (the first case) reduces the functional activity of the latter.

These are genes located in the same places (loci) of homologous chromosomes, responsible for the development of alternative traits. The interaction of allelic genes occurs only in the heterozygous state (Aa).

Variants of interaction of allelic genes:

a) total dominance

b) incomplete dominance,

c) coding

d) dominance

e) pleiotropic effect of the gene.

1 . Complete dominance. Occurs when one allele
gene (dominant) completely hides the presence of another (recessive)
allele. For example:

A - brown eyes

a blue eyes

A person with the Aa genotype has brown eyes.

2. incomplete dominance. With incomplete dominance, the phenotype
hybrids of the first generation (Aa) outwardly differ from the parent individuals
(AA) and (aa). The manifestation of the trait is intermediate compared to
parent forms.

For example, when homozygous plants with red (AA) and white (aa) flowers are crossed, first-generation hybrids have pink (Aa) flowers.

In humans, a trait that determines the shape of hair is inherited according to the type of incomplete dominance: the curly hair gene (A) incompletely dominates the straight hair gene (a), wavy hair is determined by the genotype - Aa.

3. Codominance- this is the interaction of two dominant allelic genes. For example, each of the allelic genes encodes a specific protein, and two types of protein are synthesized in a heterozygous organism. According to the type of coding in humans, the fourth blood group (I I) is inherited.

4. Overdominance - in the heterozygous state (Aa), the dominant allele is manifested to a greater extent than in the homozygous state (AA). For example, corn hybrids are characterized by higher growth, grain yield compared to homozygous plants. This phenomenon is called heterosis or hybrid vigor. In humans, according to the type of overdominance, acceleration is manifested.

5. Pleiotrolia - one gene affects the manifestation of several traits, this phenomenon is called the multiple action of one gene. For example, in humans, a well-known disease - Marfan's syndrome - arachnodactyly ("spider fingers") is determined by a dominant gene that is responsible for the pathological development of connective tissue, as a result of which a complex of pathological signs manifests itself - long, thin ("spider") fingers, defects in the development of the heart vascular system and subluxation of the lens (impaired vision). At the heart of such pathological signs is a defect in the development of connective tissue, caused by a pathological gene.

Interaction of non-allelic genes

III - I B I B l B i

IV-I A 1 B

However, there is a rare epistatic gene (<р), which in the homozygous recessive (<рд>) state suppresses all dominant alleles that determine blood groups. As a result, people with the genotype - srsr, phenotypically, only the first blood type is manifested.

For example, in people with the genotype \ A 1 A<р<р I blood group will appear, tk. 1A gene activity is blocked by a suppressor gene (R, which shows its activity in the homozygous recessive state (<рф) - The first blood group will appear in people with the following genotypes:

3. Polymerism - the manifestation of one trait, depending on the total action of several non-allelic genes. Moreover, the more dominant genes, the stronger the trait manifests itself. Polymeric genes are usually denoted by one letter of the Latin alphabet with a numerical index (A and A 2).

An example of the polymeric action of genes in humans is the inheritance of skin color. Several pairs (about five pairs) of non-alelic dominant genes responsible for the synthesis of the melanin pigment, which causes dark skin color - A |, A 2, etc. The genotypes of people with the corresponding shades of skin colors can be:

A | A | A A 2 - black skin A ^ Ar Ag - dark aia, A 2 A 2 - swarthy a! a | A 2 a 2 - light a! a, a 2 a 2 - white.

In addition to the inheritance of skin color, polymer genes in humans determine most of the quantitative traits, such as height, body weight, intellectual characteristics, a tendency to increase blood pressure, resistance to infectious diseases, and others.

Traits that are determined by several pairs of non-allelic genes are called polygenic.

Task 1. Transform active structures into passive ones:

What fills I'm sorry, what hides What/presence presence/ What depresses action what what suppresses I'm sorry, what blocks activity what.

Task 2. Write sentences, opening brackets:

1. Codominance is a phenomenon when (heterozygous state) both genes are present.

2. Complementarity is manifested when the action of one gene is complemented (action of another gene).

3. There is a rare epistatic gene (f), which in the homozygous recessive state suppresses (all dominant alleles of blood groups).

4. Gene activity is blocked (epistatic gene in the homozygous state).

What conditioned how(because...)

Task 3. Transform simple sentences into complex ones.

1. Normal hearing is due to the presence of two non-allelic DiE genes.

2. The color of the corollas of the flower is due to the presence of two dominant genes A and B.

3. Blood groups according to the ABO system are due to the inheritance of three alleles of the same type (1 A, 1B, Yu).

Task 4. Read the information. What are the differences between allelic and non-allelic genes?

a) allelic genes are genes located in the same places on homologous chromosomes. The interaction occurs only in the heterozygous state;

b) non-allelic genes are genes that are located on non-homologous chromosomes. Interaction between non-allelic genes occurs if they are responsible for the development of any one trait.

Task 5. Read text 1 "Interaction of allelic genes" and define each of the options for the interaction of allelic genes.

Task 6. Read part of the text "Epistasis" and answer the question: "What is meant by ...?"

a) epistasis;

b) dominant epistasis;

c) the "Bombay phenomenon"?

Task 7. Tell us about polymers according to the following plan.

1. Definition of polymer.

2. Dependence of the degree of manifestation of a trait on the number of dominant genes.

3. Traits determined by polymeric genes.

4. An example of the polymeric action of genes.

Solution of typical tasks

Interaction of allelic genes (incomplete dominance)

I. In humans, straight hair is a recessive trait, and curly hair does not completely dominate straight hair; wavy hair appears in heterozygotes. What kind of children can parents with wavy hair have?

Let's designate the genes:

A - curly hair

a straight hair

Aa is the human genotype with wavy hair.

Marriage pattern:

R: $Aa x s? Aa

Gametes: A, a A, a

F| : AA; Ah, Ah; aa

curly wavy straight hair hair hair

Answer: 25% of children will have curly hair (LA), 25% will have straight hair (aa) and 50% will have wavy hair (Aa).

Interaction of allelic genes (codominance)

2. A man with blood group II (homozygous) married a woman with blood group III (homozygous). Designate:

b) genotypes of parents;

c) write a scheme of marriage;

e) determine what blood types children can have;

f) what interaction of allelic genes was manifested in this situation?