Question

Examine a two-gene cross in which a mutation in HERC2 is epistatic to the OCA2 gene. In a cross between a blue-eyed OOhh woman and a blue-eyed ooHH man, what eye color will the progeny have?

a. 9 brown eyes: 7 blue eyes
b. 3 brown eyes: 1 blue eyes
c. All blue eyes
d. All brown eyes

Answer 1

In recessive epistasis, the epistatic gene -HERC2- in h0m0zyg0us recessive state inhibits the expression of the hypostatic gene -OCA2-. In the example, the F1 is heter0zyg0us for both genes. Option D. All brown eyes.

Epistasis

When talking about epistasis, we are referring to an interruption.

These are interactions between genes located in different loci in the same chromosome.

An epistatic gene can alter, influence, or suppress the expression of a hypostatic gene.

When the epistatic gene is recessive, the interaction is known as recessive epistasis.

Available data:

• Two genes
• HERC2 gene is epistatic to the OCA2 gene
• Cross:  blue-eyed OOhh woman and a blue-eyed ooHH man

We will assume that

• H allele expresses color
• h allele inhibits color
• O allele expresses brown
• o allele expresses blue.

   Genotypes                                    Phenotypes

HHOO, HhOO, HHOo, HhOo          Brown eyes

HHoo, Hhoo                                      Blue eyes

hhOO, hhOo, hhoo                           Blue eyes        

                           

Individuals that are h0m0zyg0us recessive for HERC2 have blue eyes regardless of the genotype of the OCA2 gene.

This is, the genotype hh inhibits the expression of OO, Oo and oo.

Cross:

Parentals) OOhh   x   ooHH

Gametes)  Oh, Oh, Oh, Oh

                 oH, oH, oH, oH

Punnett square)       Oh         Oh           Oh          Oh

                 oH        OoHh     OoHh     OoHh     OoHh

                 oH        OoHh     OoHh     OoHh     OoHh

                 oH        OoHh     OoHh     OoHh     OoHh

                 oH        OoHh     OoHh     OoHh     OoHh

F1) 100% of the progeny will be heter0zyg0us for both genes, expressing brown eye color.

Among the progeny, neither of the genes is in h0m0zyg0us recessive estate, meaning that the expression of brown eyes is possible.

The eye color among the progeny is expected to be 100% brown eyes. Option D.

You can learn more about epistasis at

https://brainly.com/question/1185116

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