In cocker spaniels, black coat color (B) is dominant over red (b), and solid color (S) is dominant over spotted (s). In the F₂ generation of a cross between BB ss with bb SS, what fraction of the offspring would be expected to be black and spotted? A)1/16 B)9/16 C)1/9 D)3/16 E)3/4

Question

Quizplus · Accepted Answer

The cross between BB ss and bb SS can be represented as follows:

BbSs x BbSs

FS 1 U 1 B 1 2 S 1 U 1 B 0

- BBSS: 1/4
- BbSS: 2/4
- bbSS: 1/4
- BBSs: 2/4
- BbSs: 4/4
- bbsS: 2/4
- BBss: 1/4
- Bbss: 2/4
- bbss: 1/4

To be black and spotted, an individual must carry one dominant B allele and one recessive b allele for coat color, and one dominant S allele and one recessive s allele for coat pattern. According to the Punnett square, only BbSs individuals will have this genotype, and there are 4 out of 16 individuals that have this genotype. Therefore, the fraction of offspring that would be expected to be black and spotted is 4/16 or 1/4, which is equivalent to 3/16 when reduced. Therefore, the answer is D.

In Cocker Spaniels, Black Coat Color (B) Is Dominant Over