mt2 - BICD 100, Genetics Spring 2008 
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Unformatted text preview: BICD 100, Genetics Spring 2008 
 Page 1 of 3 2nd Midterm Exam May 21, 2008 TEAR OFF THE LAST PAGE (ANSWER SHEET) AND FILL OUT. HAND ONLY IT IN. YOU MAY KEEP THE EXAM ITSELF. NO CREDIT FOR ANSWERS LEFT ON THE EXAM AND NOT PUT ON THE ANSWER SHEET. 
 
 (40 pts total) I. Please use one sentence or less to answer directly the following questions. (Remember that these questions are worth only 10 points, so be brief and to the point.) PLEASE WRITE CLEARLY (large). As an example, the difference between acrocentric and acentric: Answer: “acrocentric has a centromere off center, acentric has no centromere.” 1. 2. 3. 4. 
 What is the difference between polyploid and polytene? What is the difference between hemizygous and haploid? What is the difference between euchromatin and heterochromatin? What is the difference between sex-limited and sex-influenced?
 
 (20 pts total) II. Double True/False Questions. Please put answers on your answer sheet. Select the correct answer from the key below for each of the following sets of statements. 
 A. B. C. D. 1. Statement I is true and Statement II is true. Statement I is true, but Statement II is false. Statement I is false, but Statement II is true. Statement I is false and Statement II is false. One plant species (n = 11) and another (n = 19) produced an allotetraploid. I. The chromosome number of this allotetraploid is 30. II. The number of its nuclear linkage groups is 30. 
 2. A married couple, both of whom had normal vision produced a color-blind son. (Color-blind is an X-linked recessive). A karyotype of the boy's skin cells indicated the presence of one Barr body/cell. 
 I. The genotype of the son is XXY. II. His genotype occurred due to non-disjunction in the mother during Meiosis I. 
 
 
 BICD 100, Genetics Spring 2008 (10 pts total) Page 2 of 3 2nd Midterm Exam May 21, 2008 III. MULTIPLE CHOICE. For this problem, put your answer on the answer sheet. Two homozygous strains of corn are hybridized and then the F1 progeny crossed to each other. The two parental strains are distinguished from each other by five different genes, all of which assort independently and produce phenotypic effects independent of one another (no interactions). Assume each allele has a cumulative and equal effect on the same trait. 1. In the F2, the number of possible genotypes is: A. B. C. 25 35 (1/4)5 D. E. 210 none of the above 
 (65 pts total) IV. The ABO system of human blood groups is determined by three alleles of a single gene, iA and iB are co-dominant, O is recessive (i). If a population in genetic equilibrium (Hardy-Weinberg) has allele frequencies of i = 0.5, iA = 0.3, iB = 0.2, what are the expected frequencies of: 1. 2. 3. genotypes? blood group phenotypes? In this population, the following pedigree is found, where the letters within the symbols designate the blood group phenotypes: I A 1 O 1 A 2 B 2 A 3 B 4 II III 1 2 What is the probability that individual III-1 will be type O? 4. If III-1 is type O, what is the probability that her brother (III-2) will be AB? PLEASE PUT YOUR ANSWERS ON THE ANSWER SHEET. 
 BICD 100, Genetics Spring 2008 (65 pts total) V. Page 3 of 3 2nd Midterm Exam May 21, 2008 A particular species of plant that has been subjected to radiation for a long period of time in order to produce chromosome aberrations is then inbred for many generations until it is homozygous for all of these aberrations. It is then crossed to the original unirradiated plant and the meiotic process of the F1 hybrids was examined. It is noticed that the following structures were observed (see below), at low frequency, in Anaphase I of the hybrid: 1. 2. a cell with a dicentric chromosome (bridge) and a fragment, another cell with a dicentric chromosome with 2 bridges and 2 fragments. 1) 2) a) What kind of chromosome aberration occurred in the irradiated plant? Be specific, indicate where the centromeres are. (15pts) b) How could the dicentric (1) above form? Be specific; diagram the crossovers, etc. (25pts) c) Explain in words and with a clear diagram how the double bridge chromosome arose (2) above. Please cross out the various trial runs that you don't want graded, and just put your final answer on the answer sheet. Show the crossovers, all the strands. Label with letters A-D, label the 4 strands, starting from the top as 1, 2, 3, 4. Label the letters as A1, A2, etc. (25pts) 
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