Black fur (B) is dominant to white fur (b) in guinea pigs. An F1 cross was conducted and resulted in 100% heterozygous guinea pigs (Bb). What is the genotypic ratio outcome of the F2 generation? A. 2 BB : 1 Bb : 1 bb

B. 3 Bb : 1 bb

C. 4 Bb

D. 1 BB : 2 Bb : 1 bb

The genotypic ratio outcome of the F2 generation involving 2 heterozygous (Bb) guinea pigs would be 1 BB : 2 Bb : 1 bb

From the cross below:

                 Bb     x     Bb

               BB    Bb    Bb    bb

BB - 1

Bb - 2

bb - 1

Thus, the genotypic ratio of the F2 would be 1 BB : 2 Bb : 1 bb

More on genotypic ratios can be found here: link

D. 1 BB : 2 Bb : 1 bb

Explanation:

This question involves a single gene coding for fur color in guinea pig. Black fur (B) is dominant over white fur (b). This means that, as stated in the question, if a black fur parent (BB) is crossed with a white fur parent (bb), a 100% heterozygous offspring (Bb) with black fur will result.

If two heterozygous guinea pigs are crossed i.e. Bb × Bb, the following gametes will be produced by each heterozygous parent:

Bb = B and b

Using these gametes in a punnet square (see attached image), offsprings with the following genotypic ratio will be produced:

1 BB : 2 Bb : 1 bb

BB and Bb = black fur guinea pigs

bb = white fur guinea pigs

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