10. Women who are Rh- may encounter problems during pregnancy if they begin prod
ID: 8256 • Letter: 1
Question
10. Women who are Rh- may encounter problems during pregnancy if they begin producing antibodies against Rh+ babies. Shannon is homozygous Rh- as is her husband Ludwig. The probability that she will have problems with her third pregnancy isa. .375 b. .50 c. 0.0 d. .0625 e. .75
11. ABO blood groups in humans may be viewed as a three allele, one locus genetic system. If an A woman and a A man have four children who are A, O, O and O the parents are
a. both heterozygotes b. AA and BB c. AB and AB
d. Rh- e. AO and OO
12. In about 85 % of Europeans, known as secretors, antigen A or B is found in saliva and other bodily fluids of people who are A, B or AB. Fifteen percent of Europeans who do produce red cell antigens do not secrete; they are nonsecretors. A woman who is an AB secretor marries another AB secretor. Their first child is an A nonsecretor. This result suggests that
a. secretor is dominant b. infidelity has occurred
c. secretor is recessive d. the couple is sterile
e. b & d are both true
Explanation / Answer
10. c. They are both homozygous for Rh-, so they will both pass the Rh- allele to their children and will not have a Rh+ baby. Neither possess an allele for Rh+ so it is impossible for them to pass this trait to any progeny. 11. The parents are both heterozygotes. Blood type O is recessive and both parents must possess an O blood type allele for any of their children to be phenotypically O blood type. OO genotype = O blood type, AO genotype = A blood type. A and B are codominant, and O is recessive to both. Any individual with A blood type is either AA or AO genotypically. 12. The secretor must be dominant. If both parents are secretors and secretion is a recessive trait, all progeny must be secretors. However, if secretion is a dominant trait, it is possible to possess a recessive allele for nonsecretion. Thus secreting parents may have nonsecreting progeny if the parents are heterozygotes.
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