Gene interaction: summary, examples and exercises

Gene interaction occurs when two or more genes, located or not on the same chromosome, interact and control a trait.

Many characteristics of living things result from the interaction of several genes.

Cases of Gene Interactions

1. Epistatic gene interaction

Also called epistasis.

Occurs when a trait is conditioned by two or more genes, but one of the alleles prevents the expression of another.

In this case, we have two types of genes: o epistatic gene, which exerts the inhibitory action and the hypostatic gene, which undergoes inhibition.

Based on these two types of genes, epistasis can be:

  • dominant epistasis: when the presence of a single epistatic allele is sufficient to cause inhibition.

Example: Determination of chicken coat color

Genotypes and Phenotypes - Chicken Coat
Genotypes Phenotypes
C_ii Colored
C_I; ccI_; ccii white

The C allele conditions colored coat. The c allele conditions the white coat.

Meanwhile, the I allele prevents pigmentation. Allele I is the epistatic gene and behaves as dominant.

Thus, to display the colored coat, chickens cannot display the I allele.

  • Recessive Epistasis: when the allele that determines the epistasis acts only in a double dose.

Example: Determination of mouse coat color

Genotypes and Phenotypes - Coat in Mice
Genotypes Phenotypes
A_P_ Aguti
yyP_ black
A_pp or aapp Albino

The P allele conditions sharp fur. The A allele allows the expression of P and p.

The a allele is epistatic and its presence in a double dose determines the absence of pigments, an albino character.

2. Non-Epistatic Gene Interaction

Occurs when two or more genes interact to express a particular trait, but no allele prevents the expression of the other.

Example: Crest determination in chickens

Combinations between the different alleles can produce four types of crest: rose, pea, walnut and simple.

Genotypes and Phenotypes - Chicken Crests
Genotypes Phenotypes
RE_ Nut
R_ee pink
rrE_ Pea
rree Simple

3. Quantitative Inheritance or Polygeny

It occurs when two or more pairs of alleles add or accumulate their effects, which allows for a series of phenotypes that are different from each other.

In general, characteristics can be influenced by environmental factors.

Examples of Quantitative Inheritance are: determining the color of the wheat seed; the color of human eyes and skin; and height and weight of the human species.

Gene Interaction and Pleiotropy

THE pleiotropy it occurs when a single gene has a simultaneous effect on several traits.

This gene is called pleiotropic.

Pleiotropy is an inverse phenomenon to gene interaction.

Exercises

(FATEC-SP) - Pairs of genes, with independent segregation, can act together to determine the same phenotypic characteristic. This phenomenon is known as:

a) gene interaction
b) epistasis
c) quantitative inheritance
d) polygeny.
e) complete dominance

a) gene interaction

(UEPG-PR) - It is an inverse phenomenon to pleiotropy:

a) gene interaction
b) epistasis
c) cryptomeria
d) polyallelia
e) multiple alleles

a) gene interaction

(UNIFOR-CE) - In pumpkin, the color of the fruits is due to the following gene combinations: B_aa = yellow
B_A_ = white
bbA_ = white
drool = green
This information allows us to conclude that the gene:
a) A is epistatic about its allele
b) B is epistemic about A and about a
c) a is hypostatic in relation to A
d) b is hypostatic in relation to B
e) A is epistemic about B and about b

e) A is epistemic about B and about b

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