In cats, the Dense pigment gene, D/d, codes for melanophilin, a protein involved in the transportation and deposition of pigment

Question

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In cats, the Dense pigment gene, D/d, codes for melanophilin, a protein involved in the transportation and deposition of pigment

into a growing hair. A separate gene, M/m, is responsible for the production of the pigment, with M_ producing black pigment and mm producing brown. When a cat has two recessive d alleles, its fur is a light gray color regardless of which alleles of M/m are present.
Required:
State the phenotype and frequency for each of the following outcomes of a dihybrid cross:

a. M_D_
b. M__dd
c. mmD
d. mmdd

Biology

1 answer:

Rainbow [2.3K] · Answer 1 · 2026-03-12T04:23:02+03:00

Answer:

a. M_D_: 9/16 Individuals with black fur

b. M__dd: 3/16 Individuals with gray fur (1/16 MMdd + 2/16 Mmdd)

c. mmD_: 3/16 Individuals with brown fur (1/16 mmDD + 2/16 mmDd)

d. mmdd: 1/16 Individuals with gray fur.

Explanation:

Provided data includes:

The dense pigment gene, D, corresponds to melanophilin.
The D allele is dominant over d.
The M/m gene determines pigment production.
M is dominant over m.
With D present, M/m is expressed.
With dd, M/m is not expressed.
DDMM, DdMM, DDMm, DdMm result in black fur.
DDmm, Ddmm lead to brown fur.
ddMM, ddMm yield light gray fur.

Cross: between two dihybrids

Parental: DdMm x DdMm

Phenotype: Black-furred x Black-furred

Gametes: DM, Dm, dM, dm; DM, Dm, dM, dm

Punnet Square: DM Dm dM dm

DM DDMM DDMm DdMM DdMm

Dm DDMm DDmm DdMm Ddmm

dM DdMM DdMm ddMM ddMm

dm DdMm Ddmm ddMm ddmm

F1: 9/16 Black-furred individuals, D-M- (1/16 DDMM + 2/16 DDMm + 2/16 DdMM + 4/16 DdMm)

3/16 Brown-furred individuals, D-mm (1/16 DDmm + 2/16 Ddmm)

4/16 Gray-furred individuals, dd-- (1/16 ddMM + 1/16 ddmm + 2/16 ddMm)