Question

a brown dog crossed with a yellow dog produced 12 brown offspring. a second brown individual was obtained. when the yellow dog was crossed with this animal, six brown and six yellow offspring were born. which of the following best explains the results of the second cross?

Answer 1

The results of the second cross can be explained by the presence of different alleles for fur color in the dogs. The brown color is dominant and is determined by the presence of the W gene, while the yellow color is recessive and is determined by the presence of the Y gene. During the second cross between a yellow dog and a brown dog, offspring with different genotypes for fur color were produced, resulting in a mix of brown and yellow individuals.

Step-by-step explanation:

The results of the second cross can be explained by the presence of different alleles for fur color in the dogs. From the given information, we can deduce that the brown color is dominant and is determined by the presence of the W gene. The yellow color is recessive and is determined by the presence of the Y gene.

In the first cross between a brown dog and a yellow dog, all the offspring were brown. This suggests that the brown dog carried two dominant alleles (WW), while the yellow dog carried two recessive alleles (yy).

In the second cross between the yellow dog and the brown dog (heterozygous for fur color), the resulting offspring were a mix of brown and yellow. This can be explained by the fact that the brown dog carried one dominant allele (W) and one recessive allele (w), while the yellow dog carried two recessive alleles (yy). Therefore, the genotypes of the offspring can be WW, Ww, Yy, or yy, resulting in both brown and yellow offspring.

Answer 2

The best explanation is that the second brown individual is heterozygous (Bb) for the coat color gene.

Finding The Best Explanation Of The Results Of The Second Cross.

The result suggests that the second brown individual is heterozygous for the coat color gene.

This can be explained using the principle of Mendelian inheritance, where there are dominant and recessive alleles.

Represent the alleles for coat color as follows:

B: Brown (dominant allele)

b: Yellow (recessive allele)

The initial cross between a brown dog and a yellow dog (assuming the brown dog is heterozygous Bb) would result in 50% brown (Bb) and 50% yellow (bb) offspring.

The initial brown dog in the cross was likely homozygous dominant (BB), and the yellow dog carried a recessive allele (bb).

In the first cross:

- Brown dog (BB) x Yellow dog (bb) → Produces all brown offspring (Bb)

In the second cross:

- Second brown individual (Bb) x Yellow dog (bb) → Results in a 1:1 ratio of brown (Bb) to yellow (bb) offspring.

This pattern is consistent with Mendelian inheritance, where the presence of a dominant allele (B) leads to a brown coat color, and the recessive allele (b) results in a yellow coat color.

Now, when the second brown individual is obtained, it could be BB (homozygous dominant) or Bb (heterozygous). If it were BB, all the offspring in the second cross would be brown.

Since there are both brown and yellow offspring, it suggests that the second brown individual is Bb.