test 4 -250 - 07 - form 1 - answer key

test 4 -250 - 07 - form 1 - answer key - Exam 4 BIL 250 G...

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Exam 4, BIL 250 / G November 26, 2007 FORM 1 Name: Student ID#: I. Multiple Choice Questions (4 points each question) 1. A red-eyed (wild type) Drosophila female is crossed with a white-eyed (mutant type) male. They only generate red-eyed female and red-eyed male progenies in F1 generation. A cross between a red-eyed female and a red-eyed male in F1 generation generate the F2 progenies. Assuming the trait for eye color is sex-linked, what are the possible phenotypes of the progeny in the F2 generation? a. all red-eyed individuals b. red- and white-eyed females and red- and white-eyed males c. only red-eyed females and white-eyed males d. both red- and white-eyed males and only white-eyed females. e. none of the above 2. Nondisjunction occurs because of: a. faulty chromosome movement during mitosis. b. imprecise or incomplete pairing during mitosis. c. centromere mutation during meiosis. d. faulty chromosome movement during meiosis. 3. Which of the following is a mechanism for sex determination? a. the presence of a Y-chromosome b. the ratio of X-chromosomes to autosomes c. the lack of an X-chromosome d. the number of chromosomes (haploid and diploid) e. all of the above 4. Dosage compensation of X-linked genes in mammals is achieved by a. forming genetic mosaics in females with cells with one functional X-chromosome. b. a gene that is turned off in males that allows expression of the X-chromosome. c. the addition of methyl groups to the Y-chromosome. d. a site on a chromosome which controls X-expression called the X-hyperactivation center. e. both X-chromosomes in the female being inactivated. 5. Which of the following can affect the expression of a phenotype? a. environment b. epistasis c. incomplete penetrance d. variable expressivity e. all of the above
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6. Suppose that a cross of rabbits yields a 15:1 black:white fur ratio. If the genes that code for color are at two separate loci, what is the genotype of the white rabbit? a. AaBb b. aaBb c. aabb d. Aabb e. AABB 7. The ability to produce the M and N antigens is determined by a gene with two alleles. Heterozygotes for the trait produce both kinds of antigens. What is this an example of? a. incomplete dominance b. partial dominance c. codominance d. semidominance e. none of the above 8. A trisomy is an event where: a. a triploid organism is formed. b. there is an extra chromosome in a diploid.
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test 4 -250 - 07 - form 1 - answer key - Exam 4 BIL 250 G...

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