Question

question 15
1 point
an albino male breeds with a light gray female. they produce 7 males and 8 females. half are red and half are gray. what was the most likely skin color genotype of the male?
\\( s^r s^r \\)
\\( s^r s^g \\)
\\( s^r s^b \\)
\\( s^g s^g \\)
\\( s^g s^e \\)
\\( s^b s^e \\)
clear selection

Explanation:

Step1: Define allele conventions

Let $S^R$ = red allele, $S^G$ = light gray allele, $S^g$ = albino (recessive) allele. Albino ($S^g$) is recessive, so albino individuals must be $S^gS^g$.

Step2: Identify female genotype

Light gray female is $S^GS^G$ (homozygous, since she expresses light gray and offspring are 50% red, 50% gray).

Step3: Test male genotype

For offspring to be 50% red, 50% gray, the male must pass either $S^R$ or $S^g$. But $S^g$ paired with $S^G$ gives light gray, and $S^R$ paired with $S^G$ gives red. So the male must be $S^RS^g$: he passes $S^R$ (50% chance) to make red offspring ($S^RS^G$) and $S^g$ (50% chance) to make light gray offspring ($S^GS^g$), matching the 1:1 ratio.

Step4: Eliminate other options

• $S^RS^R$: All offspring would be $S^RS^G$ (red) → incorrect.
• $S^RS^G$: Offspring would be $S^RS^G$ (red) and $S^GS^G$ (gray) → but male is albino, can't be $S^RS^G$ (would express red/gray).
• $S^GS^G$, $S^GS^g$: Male would not be albino → incorrect.
• $S^gS^g$: All offspring would be $S^GS^g$ (gray) → incorrect.

Answer:

$S^RS^g$