Question

1. in mice, black fur (b) is dominant over brown fur (b). cross two heterozygous mice (bb × bb). complete the punnett square and find the ratios.

Explanation:

Step1: Determine gametes

The heterozygous mice (Bb) can produce two types of gametes: B and b.

Step2: Set up Punnett - square

	B	b
b	Bb	bb

Step3: Calculate phenotypic ratio

There are 3 black - fur (BB + Bb + Bb) and 1 brown - fur (bb) mice. So the phenotypic ratio of black fur to brown fur is 3:1.

Step4: Calculate genotypic ratio

There is 1 BB, 2 Bb, and 1 bb. So the genotypic ratio is BB:Bb:bb = 1:2:1.

Answer:

Phenotypic ratio: 3 black : 1 brown; Genotypic ratio: 1 BB : 2 Bb : 1 bb