Question

: In some breeds of dogs, black (B) is the result of the production of black eumelanin ( a fur pigment protein) and it is dominant over brown (b) or the production of brown eumelanin. If we cross a true breeding male black dog with a female brown dog, what are the phenotypes and genotypes of the F1 and F2? In order to solve the problem, follow the steps below while answering the questions.

Answer 1

Gentoype of F1: all Bb

Phenotype of F1: black

Genotypes and phenotypes of F2:

1/4 BB - black fur

1/2 Bb - black fur

1/4 bb - brown fur

Step-by-step explanation:

Black fur (B) is dominant over brown fur (b).

A true breeding black dog will have the genotype BB.

A true breeding brown dog will have the genotype bb.

If both of them are crossed:

BB x bb

F1 progeny: All Bb with Black fur.

At F2:

Bb x Bb

Progeny:

1 BB - black fur

2 Bb - black fur

1 bb - brown fur

Hence:

Gentoype of F1 = all Bb

Phenotype of F1 = black

Genotypes and phenotypes of F2:

1 BB - black fur

2 Bb - black fur

1 bb - brown fur