Name: ___________________________ 1 7.012 Final Exam -- 2006 You have 180 minutes to complete this exam. There are 19 pages including this cover page, the AMINO ACID page, and the GENETIC CODE page at the end of the exam. Please write your name on each page. Only writing on the FRONT of every page will be graded. (You may use the backs, but only as scratch paper.) Question 1 37 pts________ Question 2 22 pts________ Question 3 16 pts________ Question 4 19 pts________ Question 5 25 pts________ Question 6 27 pts________ Question 7 28 pts________ Question 8 26 pts________ TOTAL 200 pts________Name: ___________________________ 2 1. (37 pts) You discover 3 new yeast mutants, mutant A, mutant B, and mutant C, that all contain mutations in genes that encode enzymes that work in the pathway for tryptophan synthesis. (a, 4 pts) When you did the genetic screen that allowed you to isolate these 3 mutants, what was the mutant phenotype you were looking for and how did you assay for that? You find that mutant A is recessive. (b, 3 pts) What experiment could you have done to infer this? (c, 3 pts) What would have been the result of this experiment that led you to this conclusion? [You also find that mutants B and C are also recessive, but you do not need to tell us how this was done.] You find that mutant A and mutant B have mutations in the same gene. (d, 3 pts) What experiment could you have done to infer this? (e, 3 pts) What would have been the result of this experiment that led you to this conclusion?Name: ___________________________ 3 You find that mutant A and mutant C have mutations in different genes. (f, 3 pts) What experiment could you have done to infer this? (g, 3 pts) What would have been the result of this experiment that led you to this conclusion? [You find that mutant A accumulates Compound X and mutant C accumulates Compound Y, but you do not need to tell us how this was done.] You find that gene A acts more upstream than gene C in the pathway. (h, 3 pts) What experiment could you have done to infer this? (i, 3 pts) What would have been the result of this experiment that led you to this conclusion? You identify the gene that is mutated in mutant C. (j, 3 pts) What kind of experiment could you have done to infer this?Name: ___________________________ 4 [You find that gene A and gene C have homologs in mice, and you obtain a mouse that is homozygous for loss-of-function mutations in both gene A and gene C, but you do not need to tell us how this was done.] You find that gene A is very tightly linked to gene C. (k, 3 pts) What experiment could you have done to infer this? (l, 3 pts) What would have been the result of this experiment that led you to this conclusion? 2. (22 pts) The parents in the pedigree below already have four kids (as you can see), and they have just given birth to two more – a set of fraternal twins, one boy and one girl. Their oldest son displays a trait, indicated below by shading. This trait is caused by an inherited mutation in “gene Q.” The parents haven’t even seen their newborn twins yet, and the nurse is about to bring them in. (a, 8 pts) Assume the trait indicated by the shaded-in shape is autosomal recessive. -- What is the chance that the girl twin will have the shaded-in trait? -- What is the chance that the boy twin will have the shaded-in trait? -- What is the genotype of the father? -- What is the genotype of the mother?Name: ___________________________ 5 (b, 8 pts) Assume the trait indicated by the shaded-in shape is X-linked recessive. -- What is the chance that the girl twin will have the shaded-in trait? -- What is the chance that the boy twin will have the shaded-in trait? -- What is the genotype of the father? -- What is the genotype of the mother? (c, 6 pts) Given the above pedigree, is it possible for the trait indicated by the shading to be caused by an inherited mutation… -- on the Y chromosome? -- in the mitochondrial DNA? -- in a maternal effect gene that is found on an autosome? 3. (16 pts) You have part of the sequence of both a “wild-type” and a “mutant” DNA sequence from one region of chromosome 13 in mice. Wild-type: 5’-ACTTGCAAGCGAATC-3’ Mutant: 5’-ACTTGCTAGCGAATC-3’ (a, 4 pts) The mutation seems to have created a stop codon. However you determine that the “mutant” mouse is not at all mutant in phenotype, and produces a protein of the exact same length and sequence as each of the corresponding proteins made by the wild-type mouse. List two different reasons for why this DNA sequence change may not shorten the length of any of the mouse proteins.Name: ___________________________ 6 (b, 5 pts) What would the effect be of a single nucleotide substitution in each of the following locations in a gene on the production of the protein product of that gene? Mutation is in… Effect on protein is… the promoter the terminator the start codon the stop codon the middle of an intron (c, 3 pts) The insertion of how many nucleotides into the coding region of a gene affects the amino acid sequence of the product of that gene less than the insertion of the other numbers? Your choices are: 5, 6, or 7. (d, 4 pts) Answer “yes” or “no” to each of the four parts of this question. If a protein is normally 400 amino acids long, can you get a protein product that is 250 amino acids long as a result of: a missense mutation? ________________ a silent mutation? _________________ a nonsense mutation? ________________ a frameshift mutation? _________________Name: ___________________________ 7 4. (19 pts) The following is a diagram of the structure of an antibody, with some of its amino acids labeled to show their identities. The antibody is shown bound to one molecule of antigen, diagrammed as a squiggle. (a, 4 pts) On the above diagram of the antibody, fill in each empty box with one name of an amino acid that must be found at that site on the antibody. (b, 4 pts) On the following diagram of the antigen, fill in each box with one name of an amino acid that would allow for the strongest possible antigen-antibody interaction at that site at pH7. Glutamic acid SerineName: ___________________________ 8 (c, 3 pts) List one amino acid that would fall into each of
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