Biol. 303 EXAM I 9/22/08 Name -------------------------------------------------------------------------------------------------------------- This exam consists of 40 multiple choice questions worth 2.5 points each. On the separate answer sheet, please fill-in the single best choice for each question. Please bubble-in your name on the answer sheet, leaving a space between first and last names. Also, bubble-in the last 5 digits of your social security number under ID NUMBER beginning in the left-most column. Good luck! -------------------------------------------------------------------------------------------------------------- 1. Eukaryotic cells differ from prokaryotic cells in that A. prokaryotes do not have DNA. B. only eukaryotes have a true nucleus. C. only eukaryotic cells contain genetic material. D. eukaryotes are usually smaller than prokaryotes. 2. A certain mammalian organism has a diploid number of chromosomes equal to 48. This organism has one pair of sex chromosomes. How many autosomes does a gamete from this organism contain? A. 48 B. 46 C. 24 D. 23 Use the following information for questions 3 and 4: A diploid somatic cell from a rat has a total of 42 chromosomes. 3. What is the total number of centromeres in a rat cell in G 1? A. 42 B. 84 C. 126 D. 168 4. What is the total number of telomeres in a sperm cell from a rat? A. 21 B. 40 C. 42 D. 84
5. The part of the eukaryotic cell cycle during which chromosomes are replicated is known as: A. S phase B. G1 phase C. checkpoint D. mitosis 6. Which step of mitosis leads to significant genetic variation? A. None. Mitosis normally produces identical cells. B. Telophase C. Prophase D. Metaphase 7. An allele is A. a type of cell. B. a dominant trait. C. a form of a gene. D. an imaginary concept. 8. In each one of Mendel's dihybrid crosses, A. codominance was observed. B. the phenotypes in the F 1 generation segregated in a 3:1 ratio. C. four distinct phenotypes were observed in the F 1 generation. D. the phenotypes in the F 2 generation segregated in a 9:3:3:1 ratio. 9. Pigeons may exhibit a checkered or plain color pattern. When checkered pigeons were crossed with plain pigeons, 38 F 1 offspring were produced and they were all checkered. When the checkered F 1 offspring were crossed, 28 checkered and 9 plain offspring were produced. From this data, the simplest conclusion would be A. Plain is dominant to checkered. B. Checkered is dominant to plain. C. Checkered and plain are codominant. D. Checkered and plain assort independently
10. The figure below shows a chromosomal separation taking place. Little circles represent centromeres. The letters stand for genes; capital and lowercase stand for different alleles. 2n in this organism is 4. What process is shown? A. anaphase of mitosis B. telophase of meiosis I C. anaphase of meiosis I D. anaphase of meiosis II A B C d A b C d 11. In the figure shown above for question 10, one chromosome carries a dominant B allele while another chromosome carries a recessive b allele. The best explanation for this is that A. the two relevant chromosomes constitute a homologous pair and the cell is heterozygous. B. one of the alleles mutated spontaneously C. an exchange occurred between sister chromatids D. crossing-over occurred in prophase I of meiosis 12. A 9:3:3:1 ratio of phenotypes in the F 2 generation of a dihybrid cross A. holds true only for genes on the same chromosome. B. indicates that the dihybrid cross is basically equivalent to two independent monohybrid crosses. C. is not indicative of independent assortment. D. indicates that an epistatic relationship exists between the two genes under investigation.
13. In a cross between two plants of the following genotypes: (AaBb x AaBb), which of the following phenotypes should occur at the lowest frequency among the offspring? A. AB B. Ab C. ab D. ab 14. Regarding the cross in question 12 above, the genotype AaBB should occur at what frequency? A. 1/4 B. 1/8 C. 1/2 D. 1/16 15. Each of the following statements about meiosis is true EXCEPT A. the products of meiosis are haploid. B. most somatic cells do not enter into meiosis. C. during meiosis, crossing-over often occurs between non-homologous chromosomes. D. the complete process of meiosis requires two rounds of cell division. 16. In animals, how many functional eggs are generally produced from one round of meiosis in a female? A. one B. two C. three D. four 17. Regarding bivalents, A. they form during metaphase II of meiosis. B. they each contain one sex chromosome. C. there are n of them produced in meiosis, where n = the haploid number of chromosomes. D. they each contain a total of two chromatids.
18. What is the probability that, in an organism with a haploid number of 17, an egg will be formed that contains no chromosomes whose centromeres were derived from maternal homologs? A. (1/17) 2 B. (1/10) 17 C. (1/2) 17 D. None of the above. 19. In each of Mendel's monohybrid crosses of pea plants, the trait that disappeared in the F 1 generation but reappeared in the F 2 generation A. illustrated the principle of independent assortment. B. was a recessive trait. C. appeared in 3/4 of the plants in F 2 generation. D. None of the above. 20. A tall, violet plant is crossed with a dwarf, white plant and all of the F 1 offspring are tall, violet. The F 1 plants are selfed to produce the F 2 generation. What fraction of the F 2 generation would you expect to be tall, white? (Assume independent assortment.) A. 1/4 B. 9/16 C. 3/16 D. 1/16 21. The principle of independent assortment A. explains the 3:1 ratio of phenotypes in the F 2 generation of Mendel's dihybrid crosses. B. is hypothetical and is never really observed in nature.. C. arises from the random alignment of different chromosomes at metaphase of mitosis. D. none of the above. 22. A woman and a man are both heterozygous for freckles (the dominant condition). If they have one child, what are the chances that it will not have freckles? A. 25% B. 50% C. It will depend on the sex of the child. D. 75%
Use the following pedigree for questions 23-27: I II III 1 2 3 1 2 3 4 5 1 4 23. Could the characteristic followed in the pedigree be caused by an autosomal dominant disease? Why or why not? A. Yes, all individuals fit the autosomal dominant inheritance pattern. B. No, the offspring of I-1 and I-2 contradict an autosomal dominant inheritance. C. No, the offspring of I-3 and I-4 contradict an autosomal dominant inheritance. D. No, the offspring of II-3 and II-4 contradict an autosomal dominant inheritance. 24. If the pedigree is for an autosomal recessive characteristic, which individuals are definitely heterozygous? A. I-1, I-2, II-2, II-4 and II-5 B. I-1, I-2, I-4, III-1 C. I-1, I-2, II-4, II-5, III-1 D. II-2, II-4, II-5, II-3 25. Could the characteristics followed in the pedigree be caused by an X-linked recessive allele? A. Yes, all individuals fit the X-linked recessive inheritance pattern. B. No, the offspring of I-1 and I-2 contradict an X-linked recessive inheritance. C. No, the offspring of I-3 and I-4 contradict an X-linked recessive inheritance. D. No, the offspring of II-3 and II-4 contradict an X-linked recessive inheritance. 26. If the characteristic followed in the pedigree is autosomal recessive, what is III-1 s genotype? A. either homozygous dominant or heterozygous B. definitely heterozygous C. definitely homozygous dominant D. there s really no good way to tell 27. If the characteristic in the pedigree X-linked recessive, what is III-1 s genotype? A. hemizygous for a dominant allele B. hemizygous for a recessive allele C. heterozygous D. can t answer this question because the characteristic cannot be X-linked recessive.
28. In the cross AaBbCcDdEE x AaBbCcDdEe, how many different phenotypes should appear among the offspring? (Assume independent assortment, simple dominance/recessiveness for each gene, and no epistasis or other gene interactions.) A. 32 B. 27 C 4 D. 16 29. In the cross described in question 28, how different genotypes should be produced among the offspring? A. 8 B. 243 C. 15 D. 162 30. Red-green color blindness is X-linked recessive. A color-blind woman has a child with a man having normal vision. Which phenotype is definitely NOT expected for the child? A. color-blind female B. color-blind male C. female with normal vision D. all of the above are possible phenotypes for the child. 31. A condition in which one gene influences the expression of another gene is called A. codominance. B. dominance. C. recessiveness. D. epistasis. 32. Consider a gene with alleles "A" and "a". Suppose that the homozygous recessive genotype aa is lethal during embryonic development. Consider a second gene with alleles B and b that assorts independently from the first gene and has no interactions with the first gene. In a cross between two individuals, AaBb x AaBb, what percentage of the offspring should die during embryonic development? A. 1/2 B. 1/8 C. 1/4 D. 2/3
33. In a disputed parentage case, the child is blood type O while the mother is blood type B. What blood type would exclude a male from being the father? A. O B. A C. B D. AB 34. In sex-influenced inheritance, A. trait can be expressed in one sex only. B a given genotype produces a different phenotype in males versus females. C. a given trait is on the X chromosome. D. fathers never pass the trait to sons. 35. If a gene is subject to genomic imprinting, then A. the maternal allele is always dominant to the paternal allele. B. one inherited allele, either the maternal or paternal, is expressed while the other is silenced. C. both alleles are silenced. D. then it is on the X chromosome. 36. When two genes fail to assort independently, the term normally applied is A. Mendelian inheritance. B. incomplete dominance. C. linkage. D. complementation. 37. Which statement is true? A. two genes on the same chromosome can never assort independently from one another. B. two genes on different chromosomes will assort independently from one another. C. recombination will occur between a given pair of linked genes every time gametes are formed. D. two genes on the same chromosome will always appear to be genetically linked to one another in a dihybrid cross.
38. If the percent recombination between A and B is 25%, the percent recombination between B and C is 37%, and the percent recombination between A and C is 50%, then A. A is not linked to B. B. A and C are likely on the same chromosome. C. A and B assort independently. D. B and C are likely on different chromosomes. 39. A female fruit fly heterozygous for three linked mutant alleles a,b,c, (genotype AaBbCc) is crossed with a male fly that is homozygous recessive for all three mutant alleles. If the phenotypes of the most common offspring are ABC and abc, and the least common offspring are abc and Abc, then the order of the genes a b c on the chromosome is: A a b c B. b a c C. b c a D. not enough information to tell. 40. Assume that for the following genetic interval there is no interference. a b c 20.0 cm 25.0 cm Consider the following 3-factor (trihybrid) testcross: (abc/+++) X (abc/abc). What percent of the offspring will be the products of a double crossover? A. 45% B. 10% C. 5% D. 2.5% Piece of cake!
Answer key: Q: 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15,16,17,18,19,20,21 A: B, D, A, C, A, A, C, D, B, D, D, B, D, B, C, A, C, C, B, C, D Q: 22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40 A: A, B, C, A, B, A, D, D, A, D, C, D, B, B, C, B, B, B, C