Bisc403

iBISC403 Genetics and Evolutionary Biology Exam 2, March 22, 2012 Instructions: 1. Grid in your name on the answer sheet. 2. DO NOT grid in your student number, the course number or section. 3. Print your last name at the top of this cover page and short answer pages. 4. At the end of the exam, turn in your exam and your answer sheet together. All multiple choice questions are of equal value and together are worth 80% of the exam. The three short answer questions are each of indicated value and worth 20% of the exam.

BISC403 Exam 2, 3-22-12

1. Suppose an individual is heterozygous for a pair of alleles (e.g., A/a). Under what conditions would a double crossover in a somatic cell of this individual lead to a clone of cells homozygous
Assume that in a specific organism, the DNA polymerase has an error rate of 1 mistake in every 106 bases copied. However, the overall mutation rate is much lower. This is most likely because: A) the polymerase is more careful in replicating regions where genes exist. B) recombination mechanisms correct errors made by the polymerase. C) not all mutations can be detected easily. D) the DNA polymerase has a proofreading function. E) mutations do not occur if mutagens are not present. Ans: D 20. Assume that a new low-calorie sweetener is developed. The structure is novel and is tested with the Ames test for mutagenicity. The following results are obtained: Sample Number of his+ revertent colonies distilled water 2 distilled water + rat liver enzymes 3 sweetener 5 sweetener + rat liver enzymes 65 What conclusion is most consistent with this data? A) The sweetener is not mutagenic. B) Rat liver enzymes are highly mutagenic. C) The sweetener is not mutagenic but can be converted into strong mutagens. D) The sweetener is mutagenic and can be converted into strong mutagens. E) The sweetener and its conversion products are equally mutagenic. Ans: C 21. Mutations that yield a partial loss of function encoded by the wild-type allele are known as: A) null mutations. B) hypomorphic mutations. C) hypermorphic mutations. D) conditional mutations. E) neomorphic mutations. Ans:
Consider the pathway for the synthesis of the amino acid arginine in Neurospora: ARG-E ARG-F ARG-H ornithine → citrulline → argininosuccinate → arginine Mutant strains of Neurospora are grown in minimal media supplements as follows. Strains may carry more than one mutation. Growth is shown by (+) no growth is shown by (o). Supplements mutant nothing ornitihine citrulline argininoarginine strain succinate a o o o o + Indicate the most accurate statement regarding strain A. A) There is a mutation in ARG-H, if citrulline accumulates, ARG-F is also defective. B) There is a mutation in ARG-H, if ornithine accumulates, ARG-F is also defective. C) There is a mutation in ARG-H, if argininosuccinate accumulates, ARG-F is also defective. D) There is a mutation in ARG-H, if citrulline accumulates, ARG-E is also defective. E) There is a mutation in ARG-E, if citrulline accumulates, ARG-F is also defective. Ans: A 23. Shown below are the deletion maps of a series of rII- mutations. The deleted region is indicated as (......) and the intact region as ______. 1 ___________(...........)_______________ 2 _________________(...........)_________ 3 (.....................)_______________ ______ 4 ________________________(................) 5 _____(..........)______________________ A series of point mutations A-E is used in a coinfection experiment. Shown below are the results of those coinfections. Ability to produce wild-type progeny phage is indicated by (+), (o)