T6 Assignment TA - Biology 2C03: Genetics Tutorial 6...

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Biology 2C03: Genetics Tutorial 6 Linkage and recombination 1. A testcross is performed on an individual to examine three linked genes. The most frequent phenotypes of the progeny were Abc and aBC , and the least frequent phenotypes were abc and ABC . (1 mark) a. What was the genotype of the individual tested? (0.25 marks) b. What is the order of the gene loci? (0.25 marks) c. Indicate the genotypes of each progeny class.(0.5 marks) a. Abc / aBC b. CAB c. cAb/cab; CaB/cab; caB/cab; CAb/cab; cAB/cab; Cab/cab; CAB/cab; cab/cab . 2. In corn, small pollen ( sp ) is recessive to normal pollen ( sp + ) and banded necrotic tissue, called zebra necrotic ( zn ), is recessive to normal tissue ( zn + ). The genes that produce these phenotypes are closely linked on chromosome 10. If no crossing over occurs between these two loci, give the types of progeny expected from the following crosses: (1 mark) a. × b. × c. × d. × a. sp + zn + / sp zn ; sp zn / sp zn b. sp + zn / sp zn ; sp zn + / sp zn c. sp + zn + / sp + zn + ; sp + zn + / sp zn ; sp zn / sp zn d. sp + zn / sp + zn ; sp + zn / sp zn + ; sp zn + / sp + zn ; sp zn + / sp zn + 3. In Drosophila melanogaster , cut wings ( ct ) is recessive to normal wings ( ct + ), sable body ( s ) is recessive to gray body ( s + ), and vermilion eyes ( v ) is recessive to red eyes ( v + ). All three recessive mutations are X- linked. A female fly with cut wings, sable body, and vermilion eyes is crossed to a male with normal wings, gray body, and red eyes. The F 1
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T6 Assignment TA - Biology 2C03: Genetics Tutorial 6...

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