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Human ABO blood type is determined by three alleles, two of which (IA and IB) produce gene products that modify the antigen produced by protein activity of an independently assorting H gene. A rare abnormality known as the Bombay
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Genetic Analysis: An Integrated Approach (2nd Edition)
- Several genes in humans in addition to the ABO gene(I) give rise to recognizable antigens on the surface ofred blood cells. The MN and Rh genes are two examples. The Rh locus can contain either a positive or anegative allele, with positive being dominant to negative. M and N are codominant alleles of the MN gene.The following chart shows several mothers and theirchildren. For each mother-child pair, choose the fatherof the child from among the males in the right column, assuming one child per male.Mother Child Malesa. O M Rh(pos) B MN Rh(neg) O M Rh(neg)b. B MN Rh(neg) O N Rh(neg) A M Rh(pos)c. O M Rh(pos) A M Rh(neg) O MN Rh(pos)d. AB N Rh(neg) B MN Rh(neg) B MN Rh(pos)arrow_forwardMutations in the genes for clotting factor VIII and IX cause hemophilia A and B, respectively. A woman may be heterozygous for mutations in both genes, with a mutated factor VIII allele on one X chromosome, and a mutated factor IX allele on the other. All of her sons should have either hemophilia A or B. However, on rare occasions, one of these women gives birth to a son who does not have hemophilia, and his one X chromosome does not have either mutated allele. Explain.arrow_forwardThe human blood alleles for both A and B blood, when expressed together are referred to asarrow_forward
- Sickle cell anemia follows a single-gene pattern of inheritance, with two alleles: one allele (S) produces normal hemoglobin, and the other (s) produces abnormal hemoglobin. Describe the phenotype outcome for each of the three possible genotypes (SS, Ss and ss), with regard to sickle cell anemia and malaria.arrow_forwardAnother blood disease, hemophilia, is caused by the failure of blood to clot. The genetic basis for the disease is due to one of two dysfunctional clotting factor genes, recessive alleles that lead to the disorders hemophilia A and hemophilia B. Due to the long history of arranged European royal marriages within a relatively small sample population, the prevalence of both hemophilia and G6PD-deficiency disorder are both high. In fact, in certain family lines sons, but not daughters, are nearly always either born with both G6PD-deficiency and hemophilia A-disease or are born completely healthy. In other family lines sons, but not daughters, are born about a quarter of the time with both G6PD-deficiency and hemophilia B. (G = G6PD gene, A = Hemophilia A, and B = Hemophilia B, X = X chromosome, Y = Y chromosome) Which of the following arrangement of loci on chromosomes best explains these observations? A B C D or Earrow_forwardThe ABO blood groups in humans are expressed as the I A , I B , and i alleles. The I A allele encodes the A blood group antigen, I B encodes B, and i encodes O. Both A and B are dominant to O. If a heterozygous blood type A parent (I A i) and a heterozygous blood type B parent (I B i) mate, one quarter of their offspring are expected to have the AB blood type (I A I B ) in which both antigens are expressed equally. Therefore, ABO blood groups are an example of: a. multiple alleles and incomplete dominance b. codominance and incomplete dominance c. incomplete dominance only d. multiple alleles and codominancearrow_forward
- Spherocytosis is an inherited blood disease in whichthe erythrocytes (red blood cells) are spherical insteadof biconcave. This condition can be inherited in adominant fashion, with ANK1 (the nonfunctional mutant allele) dominant to ANK1+. In people with spherocytosis, the spleen recognizes the spherical redblood cells as defective and removes them from thebloodstream, leading to anemia. The spleen in different people removes the spherical erythrocytes withdifferent efficiencies. Some people with sphericalerythrocytes suffer severe anemia and some mild anemia, yet others have spleens that function so poorly nosymptoms of anemia exist at all. When 2400 peoplewith the genotype ANK1 ANK1+ were examined, itwas found that all of them had spherical erythrocytes,2250 had anemia of varying severity, and 150 had nosymptoms. (Assume that ANK1 ANK1 homozygotesdo not exist.)a. Does this description of people with spherocytosisrepresent incomplete penetrance, variable expressivity, or both? Explain…arrow_forwardWith regard to the ABO blood types in humans, determine thegenotypes of the male parent and female parent: Male parent: blood type B whose mother was type OFemale parent: blood type A whose father was type B Predict the blood types of the offspring that this couple may have and the expected ratio of each.arrow_forwardSpherocytosis is an inherited blood disease in which erythrocytes (red blood cells) are spherical instead of biconcave. This condition is inherited in a dominant fashion, with ANK1 (the nonfunctional mutant allele) dominant to ANK1+. In people with spherocytosis, the spleen recognizes the spherical red blood cells as defective and removes them from the bloodstream, leading to anemia; this removal occurs with different efficiency in different people. Some people with spherical erythrocytes suffer severe anemia, some have mild anemia, and others do not have any symptoms of anemia. When 2400 people with the genotype ANK1/ANK1+ were examined, it was found that all of them had spherical erythrocytes, 2250 had anemia of varying severity, and 150 had no anemia symptoms. The ANK1/ANK1 genotype is never observed. Which evidence suggests that spherocytosis is incompletely penetrant?arrow_forward
- The XG locus on the human X chromosome has twoalleles, XG+ and XG. The XG+ allele causes the presence of the Xg surface antigen on red blood cells,while the recessive XG allele does not allow antigento appear. The XG locus is 10 m.u. from the STSlocus. The STS+ allele produces normal activity ofthe enzyme steroid sulfatase, while the recessive STSallele results in the lack of steroid sulfatase activityand the disease ichthyosis (scaly skin). A man withichthyosis and no Xg antigen has a normal daughterwith Xg antigen. This daughter is expecting a child.a. If the child is a son, what is the probability he willlack Xg antigen and have ichthyosis?b. What is the probability that a son would have boththe antigen and ichthyosis?c. If the child is a son with ichthyosis, what is theprobability he will have Xg antigen?arrow_forwardWhich of the following statements is/are true and which is/are false? The expression of lethal genes in heterozygotes is called penetrance. Expressivity is the balanced genetic output from a hemizygous condition.arrow_forwardIn humans, blood type AB is a codominant trait. Suppose Jim has blood type AB (IAIB) and his wife has blood type O (ii). What are the possible genotypes and blood types of their children?arrow_forward
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