Question

a cross was performed, and the offspring shown to the right were produced. what is the most likely genotype for the parents? bbee × bbee bbee × bbee bbee × bbee bbee × bbee 10 mice with black fur, black eyes 2 mice with black fur, red eyes 3 mice with white fur, black eyes 1 mouse with white fur, red eyes

Explanation:

Step1: Analyze the ratio of offspring

The ratio of black fur : white fur is \((10 + 2):(3+1)=12:4 = 3:1\). The ratio of black eyes : red eyes is \((10+3):(2 + 1)=13:3\approx3:1\).

Step2: Recall Mendelian genetics

A \(3:1\) ratio for a single - trait cross (assuming complete dominance) is expected when both parents are heterozygous for that trait.

Step3: Check each option

• For \(Bbee\times bbEE\):
• For fur color (\(B/b\)): \(Bbee\times bbEE\) gives \(Bb:bb = 1:1\) (not \(3:1\)).
• For \(BbEE\times Bbee\):
• For eye color (\(E/e\)): \(BbEE\times Bbee\) gives \(EE:Ee = 1:1\) (not \(3:1\)).
• For \(BbEe\times BbEe\):
• Using the Punnett square or the product rule. For fur color (\(B/b\)): \(Bb\times Bb\) gives \(BB:Bb:bb=1:2:1\), so the ratio of black (\(BB + Bb\)) to white (\(bb\)) is \(3:1\). For eye color (\(E/e\)): \(Ee\times Ee\) gives \(EE:Ee:ee = 1:2:1\), the ratio of black (\(EE + Ee\)) to red (\(ee\)) is \(3:1\).
• For \(BBEE\times bbee\):
• All offspring will be \(BbEe\) (not showing the \(3:1\) ratio for either trait in the offspring as shown in the problem).

Answer:

C. \(BbEe\times BbEe\)