In a cross with a mother who carries the allele for hemophilia and a father who has normal blood clotting what would be the expected phenotypes of the offspring?
A. all females normal, all males normal
B. all females normal, all males with hemophilia
C. all females carriers of hemophilia, all males normal
D. one female normal, one male normal, one female carrier, one male with hemophilia
here's my work:
XCXC, XcY
XCXc, XCXc, XCY, XCY
doesnt this mean that all the girls have hemophilia, and all the boys are normal?
The girls all receive normal X chromosome from dad, meaning they cannot be more than carriers. If males get recessive gene, they will have hemophilia since there is no dominant gene on the Y chromosome to supress the hemophilia gene.
How do you get six variations?
XCXC, XcY
XCXc, XCY
Based on your work, it seems there was a slight mistake in your crosses. Let's revise it step-by-step to determine the expected phenotypes of the offspring of a mother who is a carrier for hemophilia (XCXc) and a father with normal blood clotting (XCY).
The mother can produce two types of gametes: XC and Xc.
The father can produce two types of gametes: XC and Y.
Crossing the mother's gametes (XC, Xc) with the father's gametes (XC, Y), we get the following possibilities for the offspring:
1. XC XC: Female offspring - normal blood clotting (not a carrier)
2. XC Y: Male offspring - normal blood clotting
3. Xc XC: Female offspring - normal blood clotting (not a carrier)
4. Xc Y: Male offspring - hemophilia
Therefore, the correct answer is:
D. one female normal, one male normal, one female carrier, one male with hemophilia.
To summarize:
- One female offspring will have normal blood clotting (not a carrier).
- One male offspring will have normal blood clotting.
- One female offspring will be a carrier for hemophilia.
- One male offspring will have hemophilia.
Based on your work, your understanding of the genotypes is correct. However, the phenotypes you have identified are incorrect.
The mother is a carrier of the hemophilia allele, denoted as XCXc, and the father is normal, denoted as XCY. When they have offspring, each child receives one allele from each parent.
Let's consider the possible genotypes and their corresponding phenotypes:
1. XCXc (mother's allele) + XCY (father's allele) = XCXCY
This results in a daughter who is a carrier but does not have hemophilia. She is phenotypically normal.
2. XCXc (mother's allele) + XCY (father's allele) = XCXCY
This results in a son who has normal blood clotting and is phenotypically normal.
3. XCXc (mother's allele) + XcY (father's allele) = XCXcY
This results in a son who has hemophilia and displays the hemophilic phenotype.
Therefore, the correct answer is:
D. one female normal, one male normal, one female carrier, one male with hemophilia