Question

in the cross bb x bb (two heterozygous mice), what percentage of the offspring would you predict to have the same phenotype as the parents?
a) 0%
b) 25%
c) 50%
d) 75%
e) 100%

next, you perform a cross with a mouse with black fur and a mouse with white fur which resulted in the offspring which confirm that the mouse with black fur was heterozygous?
a) 4 mice with black fur
b) 8 mice with black fur, 1 mouse with white fur
c) 5 mice with black fur, 0 mice with white fur
d) 6 mice with black fur, 2 mice with white fur
done

Explanation:

Step1: Set up Punnett - square

The cross is Bb x bb. The possible gametes from Bb are B and b, and from bb are b.

Step2: Fill in Punnett - square

	B	b
b	Bb	bb

Step3: Determine genotypes and phenotypes

Genotypes are Bb:bb = 1:1. If B represents black fur (dominant) and b represents white fur (recessive), the phenotypes are black - furred (Bb) and white - furred (bb) in a 1:1 ratio.

Step4: Calculate percentage of offspring with parental phenotypes

One parent has black fur (Bb) and the other has white fur (bb). The percentage of offspring with the same phenotypes as the parents is 50% (Bb) + 50% (bb) = 50%.

Answer:

50%