Problem Sets Fall 1999 mutants of mating type o 1 1 2 3 4 5 2 mutants of matingtypea 3 4 5 Give as much information as you can about your new canavanine resistant mutations Indicate which mutations are dominant and which are recessive also state how many genes are representedandwhich mutationslie the same gene Again assumeeach strain carries only a single mutation 2 A hypothetical insect has blue eyes but mutant insectsthat can not form blue pigment have white eyes Production of blue pigment involves the activities of enzyme A and enzyme B both encoded by autosomal genes First suppose that the pathway for production of blue pigment involves enzyme A and enzyme B operating in series Enzyme A Enzyme B Bluepigment a A true breeding strain with a recessive mutation in the gene for enzyme A is crossed to a true breeding strain with a recessivemutationin the gene for enzyme B Will the resulting F1 progeny have blue or white eyes When these F1 insects are then crossed among themselves what will the phenotypic ratio of blue to white eyed insects be among the F2 I b A true breeding strain with a dominant mutation in the gene for enzyme A is crossed to a true breeding strain with a dominant mutationin the gene for enzyme B Will the resulting F1 progeny have blue or white eyes When these F1 insects are then crossed among themselves what will the phenotypic ratio of blue to white eyed insects be among the F2 J c A true breeding strain with a recessive mutation in the gene for enzyme A is crossed to a true breeding strain with a dominant mutation in the gene for enzyme B Will the resulting F1 progeny have blue or white eyes When these F1 insects are then crossed among themselves what will the phenotypic ratio of blue to white eyed insects be among the F2 Now suppose that enzyme A and enzyme B act in parallel That is there are two different ways to make blue pigment and white eyed insects only result when the steps carried out by both enzyme A and enzyme B are inactive Enzyme A Enzyme B Blue pigment d A true breeding strain with a recessive mutation in the gene for enzyme A is crossed to a true breeding strain with a dominant mutation in the gene for enzyme B Given the parallel pathway model will the resulting F1 progeny have btue or white eyes When these F1 insects are then crossed among themselves eyed insects be among the F2 what will the phenotypic ratio of blue to white e Let s say that you are trying to distinguish the series model in part c from the parallel pathway model in part d but you decide to look at only eight flies from the F2 generation Apply the chi square test to all nine possible phenotypic ratios for eight flies to determine which observed ratios are consistent with the expected ratios for each of the two models Use the criteria that the hypothesis can be rejected only if the p value is 0 05 How many of the possible outcomes will not definitively distinguish the two models f Finally suppose that the gene for enzyme A is on the X chromosome and that the gene for enzyme B is autosomal Both males and females from a true breeding strain with a recessive mutation in the gene for enzyme A are crossed to females and males from a true breeding strain with a dominant mutation in the gene for enzyme B Given the parallel pathway model and the sex linkage of gene A will the F1 progeny have blue or white eyes Specify males or females When the F1insects are then crossed among themselves what will the phenotypic ratio of blue to white eyed insects be among males in the F2 What will the phenotypic ratio be for females in the F2 3 You have just been hired as a genetic counselor for a royaJ family that still engages in a significantamount of inbreeding As your first assignmentyou are presented with the following pedigree where the filled symbol represents a male in the royal family who has a rare recessive disease Your job is to calculate the probability that the child indicated by will have the disease do this assume that no new mutations arise within the pedigree and that no unrelated individualis a carrier becausethis is a very raredisease a tf the disease is caused by an autosomal recessive the child indicated by will have the disease allele what is the probability To that b If the disease is caused by an X linked recessive allele what is the probability that a son will have the disease What is the probability that a daughter will have the disease c If the disease is caused by an autosomat recessive allele and the first child has the disease what is the probability that the second child will have the disease 7 03 Problem FA1999 Set 1 Solutions la Mutant 3 fails to complement with any other strain but carries only a single mutation that this strain carries a dominant mutation It is likely Mutants 1 and 5 are recessive mutations in the same complementation group They are probably alleles of the same gene Mutant 2 is a recessive mutation in its own complementation group as it complements the rest of the mutants It is in a separate gene from the rest Mutant 4 is a recessive mutation in its own complementation group in a separate gene from the rest Our set of strains represent mutations in 3 or 4 different genes with the ambiguity due to mutant 3 being dominant By this test we can not determine in which gene mutant 3 is in lb Mutant 4 fails to complement with any other strain but carries only a single mutation that this strain carries a dominant mutation It is likely Mutants 1 and 2 are recessive mutations in the same complementation group They are probably alleles of the same gene Mutant 3 is a recessive mutation in its own complementation group as it complements the rest of the mutants It is in a separate gene from the rest Mutant 5 is a recessive mutation in its own complementation group in a separate gene from the rest Our set of strains represent mutations in 3 or 4 different genes with the ambiguity due to mutant 4 being dominant By this test we can not determine in which gene mutant 4 is in 2a All the F I progeny will have blue eyes Both mutations thus the two strains will complement are recessive each other in the F I generation gives a ratio of 9 7 blue to white eyed progeny to the wild type allele and Using the punnet square for the F generation AB Ab aB ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb ab AaBb Aabb aaBb aabb Only progeny with either 2 a alleles or 2 b alleles or both will produce white eyed flies 2b All the F1 progeny will have …
View Full Document
Unlocking...