Question

8. The F8 gene is located on the X chromosome. It is used by cells in the liver to produce coagulation factor VIII that is released into the bloodstream where it functions in blood clotting. An inability to produce this protein is a common cause of hemophilia. A woman inherited a null allele (no functional product from her father, and a functional allele from her mother. a. Does this woman produce the coagulation factor? (mark answer with an X) No Yes b. Which of the following correctly describes the expression of the F8 gene: Only the maternal copy of the gene is expressed in all of the cells. The maternal copy of the gene is expressed in approximately half of the cells, and the paternal copy of the gene is expressed in the other cells. Only the paternal copy of the gene is expressed in all of the cells. c. Explain what causes that pattern of expression.

Answer 1

a. YES.

b. 2 : The maternal expression of the gene is expressed in approximately half of the cells, and the maternal copy of the genes are expressed in the other cells .

c. Carrier females have about half the usual amount of coagulation factor VIII which is generally enough for normal blood clotting. However, about 10 percent of carrier females have less than half the normal amount of one of these coagulation factors; these individuals are at risk for abnormal bleeding, particularly after an injury, surgery, etc. Expression of the X chromosome is dependent on both the female and male parents in the case of having a daughter hence the daughters are usually recessive.