Questions: Next, you perform a cross with a mouse with black fur and a mouse with white fur. Which result(s) for the offspring would confirm that the mouse with black fur was heterozygous? 4 mice with black fur 8 mice with black fur, 1 mouse with white fur 5 mice with black fur, 6 mice with white fur 6 mice with black fur, 2 mice with white fur

The question is asking which result(s) for the offspring would confirm that the mouse with black fur was heterozygous when crossed with a mouse with white fur.

To determine this, we need to understand the genetic principles involved. Let's assume that black fur (B) is dominant over white fur (b). A heterozygous black-furred mouse would have the genotype Bb, while a white-furred mouse would have the genotype bb.

When a Bb mouse is crossed with a bb mouse, the possible genotypes of the offspring are:

• Bb (black fur)
• bb (white fur)

The expected ratio of phenotypes (fur color) in the offspring would be:

• 50% black fur (Bb)
• 50% white fur (bb)

Now, let's analyze each option:

1. 4 mice with black fur:

   • This result does not fit the expected 1:1 ratio of black to white fur. It suggests that all offspring have black fur, which would be more likely if the black-furred parent were homozygous (BB).

2. 8 mice with black fur, 1 mouse with white fur:

   • This result does not fit the expected 1:1 ratio. The ratio here is 8:1, which is not consistent with a Bb x bb cross.

3. 5 mice with black fur, 6 mice with white fur:

   • This result is close to the expected 1:1 ratio. The slight deviation can be attributed to natural variation in small sample sizes.

4. 6 mice with black fur, 2 mice with white fur:

   • This result does not fit the expected 1:1 ratio. The ratio here is 3:1, which is more consistent with a Bb x Bb cross rather than a Bb x bb cross.

The answer is the third one: 5 mice with black fur, 6 mice with white fur.

Explanation:

• 4 mice with black fur: Incorrect, as it suggests a homozygous black-furred parent.
• 8 mice with black fur, 1 mouse with white fur: Incorrect, as the ratio is not consistent with a Bb x bb cross.
• 5 mice with black fur, 6 mice with white fur: Correct, as it is close to the expected 1:1 ratio.
• 6 mice with black fur, 2 mice with white fur: Incorrect, as the ratio is more consistent with a Bb x Bb cross.