1. Hemophilia is a blood disorder in which the blood does not clot properly. It
ID: 214575 • Letter: 1
Question
1. Hemophilia is a blood disorder in which the blood does not clot properly. It is a recessive trait which is sex-linked, i.e. it is inherited along with the X-chromosome. Because men have only one X chro- mosome any gene present on their X chromosome will be expressed. A normal woman who is a carrier for hemophilia marries a normal man. a) What are the possible genotypes of their children?* b) What are the phenotypic ratios? c) What is the probability that a daughter will have hemophilia? The probability a son will have hemophilia? What is the probability that if the parents conceive that the child (sex unknown) will have hemophilia? **Note: In figuring this problem remember that the X and Y chromosome synapse and segregate as a pair in meiosis. Therefore, the Y chromosome should be used as the allele of the hemophil- iac or normal blood clotting gene in determining the offspring.Explanation / Answer
1. Woman's genotype - XHXh
Man's genotype - XHY
Punnett square analysis:
a. The possible genotypes of their children are - XHXH, XHY, XHXh, XhY
b. The phenotypic ratio are - normal female : carrier female : normal male : normal male = 1:1:1:1
c. There is 0% probability that a daughter will have hemophilia. There is 50% probability that a son will have hemophilia.
d. Since out of four children, one will suffer from hemophilia, so there are 25% chances that if the parents conceive that their child (unknown sex) will have hemophilia.
XH Xh XH XHXH (normal female) XHXh (carrier female) Y XHY (normal male) XhY (normal male)Related Questions
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