. The hemophilia gene is located 12 map units from the red-green colorblindness gene on the X chromosome. Red-green colorblindness is recessive to normal color vision. A woman with normal blood clotting and normal color vision, but whose father was a hemophiliac and whose mother was red-green colorblind, marries a man who is not a hemophiliac and is not colorblind. What percent of their children will be colorblind and have hemophilia? Show your work and warrant your claim
To determine the percentage of their children who will be colorblind and have hemophilia, we need to consider the inheritance patterns of both traits. Let's break down the problem step by step:
1. We know that hemophilia (H) is located 12 map units away from the red-green colorblindness (C) gene on the X chromosome. This distance indicates that these two genes are not linked closely and tend to assort independently during meiosis.
2. The woman in question has a normal blood clotting phenotype, so she must carry at least one normal allele for the hemophilia gene (H+). Her father was a hemophiliac, meaning he contributed a hemophilia allele (H) to his daughter.
3. The woman's mother was red-green colorblind, which means she carried two recessive alleles for the colorblindness gene (C-). Therefore, this woman must have inherited one recessive allele for the colorblindness gene (C-) from her mother.
4. The man she marries is not hemophiliac and not colorblind, implying that he must have inherited a normal allele for both traits (H+ and C+).
Now, let's consider the different possible combinations of alleles in their offspring:
1. Sons:
- There is a 50% chance that a son will inherit the hemophilia allele (H) from the mother.
- There is a 0% chance a son will inherit the colorblindness allele (C-) from the mother since the father does not carry it.
- Therefore, all sons will be normal for color vision (C+) but have a 50% chance of being hemophiliac (H).
2. Daughters:
- There is also a 50% chance that a daughter will inherit the hemophilia allele (H) from the mother.
- There is a 50% chance that a daughter will inherit the colorblindness allele (C-) from the mother.
- Since the father does not have these alleles, daughters will only inherit the alleles (H+ and C+) from the father.
- Therefore, all daughters will be carriers for hemophilia (H+) and normal for color vision (C+).
To summarize, their offspring will have the following:
- 50% chance of sons who are normal for color vision (C+) with a 50% chance of being hemophiliac (H).
- 50% chance of daughters who are carriers for hemophilia (H+) and normal for color vision (C+).
In conclusion, none of their children will be both colorblind and hemophiliac.