if a homozygous white horse and a homozygous black horse were bred together
, what percentage of the offspring will be roan and express both colors in their hair?
a. 100%
b. 50%
c. 0%
d. 25%
The coloration of a horse's coat, including roan, is influenced by genetics. The roan coat pattern in horses is typically characterized by a mixture of colored and white hairs on the body, while the head, mane, tail, and lower legs tend to be solid in color.
In horses, roan is a simple dominant trait governed by a specific gene locus, where the roan allele (let's call it "R") is dominant over the non-roan allele (let's denote it as "r"). When a roan horse (Rr) is bred, it can pass on either the roan allele (R) or the non-roan allele (r) to its offspring.
If both parents are homozygous for their respective colors and do not carry the roan allele (meaning they are rr, with "r" representing the absence of roan), then no offspring can be roan because neither parent can contribute the dominant roan allele.
So if you have:
- A homozygous white horse (rr white)
- A homozygous black horse (rr black)
None of the offspring can be roan because the roan allele is not present in either parent. The offspring would inherit an "r" allele from each parent, making them "rr" non-roan (either black, white, or another color dependent on the specific genetic interaction of the coat color genes, but definitely not roan).
Therefore, the correct answer is:
c. 0%