In rats, gene B produces black coat color if the genotype is B-, but black pigme

Question

In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced if the genotype is bb. At an independent locus, gene D produces yellow pigment if the genotype is D-, but no pigment is produced when the genotype is dd. Production of both pigments results in brown coat color. If neither pigment is produced, coat color is cream. A third independently assorting gene involved in determination of coat color in rats is the C gene. At this locus, the genotype C- permits expression of pigment from genes B and D. The cc genotype, however, prevents expression of coat color and results in albino rats. For each of the following crosses, determine the expected phenotypes and their ratio in progeny:

Explanation / Answer

Considering pure line,

the parents genotypes would be as follows

BBDDCC X bbddcc

and the set of alleles involved as follows: -

B_ = black pigment

bb = black pigment not formed

D_ = yellow pigment

dd = no yellow pigment

B_D_ = Brown pigment

bbdd = cream coat color

C_ = permits black and yellow pigment formation that means it codes fro an enzyme which converts the proenzyme coded by gene B_ and D_.

cc = albino

Now,

the F1 generation would be having genotype BbDdCc

Now, F2 generation cross as follows,

BbDdCc X BbDdCc

expected number of genotype 2n where n is the no. of gene involved i.e. 23 = 8.

expected phenotypic ratio is 27:9:9:3:9:3:3:1

expexted genotypic ratio is 1:2:1:2:4:2

the expexted Genotypes-Phenotyeps are represented as follows: -

B_D_C_ = Brown

B_D_cc = albino

B_d_C_ = Black

B_d_cc = albino

b_D_C_ = Yellow

b_D_cc = albino

bbddC_ = cream

bbddcc = albino

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