(1) The genes involved in production of the blood types have been studied extensively.

Integration Problems: (1) The genes involved in production of the blood types have been studied extensively. Blood type is determined by one gene with three alleles. This gene encodes an enzyme that is involved in the synthesis of a polysaccharide on the surface of red blood cells. This enzyme is called a glycosyltransferase. The structures of the blood type antigens (the molecules that the immune system responds to when rejecting blood of an incompatible type) are shown below: The IA allele of the blood type gene encodes a glycosyltransferase enzyme that catalyzes the following reaction: (Note: UDP is uridine diphosphate, a relative of ADP.) The IB allele of the blood type gene encodes a glycosyltransferase enzyme that catalyzes the following reaction: The i allele of the blood type gene encodes a glycosyltransferase enzyme that is inactive. a) An individual with genotype ii would not have any active glycosyltransferase. Explain in terms of protein activity why an ii individual would have type O blood. b) Explain in terms of protein activity why the blood type-A phenotype of the IA allele and the blood type-B phenotype of the IB allele are dominant to the blood type-O phenotype of the i allele. That is, why do people with genotypes IAi and IBi have type A and type B blood (respectively) and not type O blood? c) Explain in terms of protein activity why the blood A type phenotype of the IA allele and the blood B type phenotype of the IB allele are codominant to each other. That is, why do people with genotype IAIB have type AB blood (both A and B) and not A, B, or something else? The i allele, which confers the recessive phenotype of type O blood, differs from the IA allele by a frameshift mutation in the coding region of the gene for the blood type-determining enzyme. The DNA sequence of the coding strand (the DNA strand that has the same sequence as the mRNA, except that T's are replaced by U's) in the appropriate region of the IA and i alleles is shown below: Sequence of IA allele: ...CGTGGTGACCCCTT... Sequence of i allele: ...CGTGGTACCCCTT... The relevant part of the sequence of the protein produced by the IA and i alleles is shown below (the differences are shown in bold): Sequence of protein encoded by IA allele: 84 85 86 87 88 89 H3N+...Leu-Val-Val-Thr-Pro-Trp-Leu...COO- Sequence of protein encoded by i allele: H3N+...Leu-Val-Val-Pro-Leu-Gly-Trp...COO- d) Based on the protein sequence data, indicate the reading frame of the DNA sequences above. That is, match the DNA sequences with their respective protein sequences. Note that the beginning of the reading frame must be the same in both sequences, starting from the left. The IA and IB alleles differ by several point mutations, resulting in four amino acid changes in the encoded proteins. These changes are listed below: Position in Polypeptide Chain Amino Acid in IA Allele Amino Acid in IB Allele 176 Arg Gly 235 Gly Ser 266 Leu Met 268 Gly Ala The DNA sequence of the coding strand in the region which encodes amino acids 266 and 268 of the IA and IB alleles is shown below (differences shown in bold underlined type): Sequence of IA allele: ...ACTACCTGGGGGGGTTCTT... Sequence of IB allele: ...ACTACATGGGGGCGTTCTT... e) Based on the mutation data, indicate the reading frame of the DNA sequences above.