In the rat, coat color is affected by a gene on chromosome 5 which has two allel

Question

In the rat, coat color is affected by a gene on chromosome 5 which has two alleles, B for black and b for brown. Black is dominant to brown. Another gene on chromosome 14 affects the pattern of coat color. This gene has two alleles. PH is the allele for hooded, in which the animal is mostly white with color restricted to the shoulders and neck. P+ is the normal solid body color allele. These two alleles exhibit incomplete dominance, so that heterozygotes are mostly colored but have white bellies.

Suppose that a true-breeding black hooded strain is crossed with a true breeding brown solid colored strain. The F1 generation rats are then intercrossed to produce an F2 generation. What phenotypes will there be in the F2 generation and in what portions are they expected?

Solve this using fork-lined method.

Explanation / Answer

here we are crossing black hooded with brown solid colored therefore the genotypes would be:

BBPHPH X bbP+P+

When these cross, the F1 generation would all be Bb PHP+giving us 4 types of gametes, which will cross like this

Therefore the final ratio of phenotypes would be

black & White with color restricted to the shoulders & neck , black & colorful & white bellies , black & solid body colors , brown & colorful & white bellies , brown & solid body colors in the ratio

4:6:3:2:1

Gametes BPH BP+ bPH bP+ BPH BBPHPH BBPHP+ BbPHPH BbPHP+ BP+ BBPHP+ BBP+P+ BbPHP+ BbP+P+ bPH BbPHPH BbPHP+ bbPHPH bbPHP+ bP+ BbPHP+ BbP+P+ bbPHP+ bbP+P+

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