Biol 331 Genetics Exam 1a Fall 2016

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1 Biol 331 Genetics Exam 1a Fall 2016 Multiple Choice. (2points each) 1. An allele is. A. one of the bases in DNA B. an alternate form of a gene C. another term for epistasis D. present only in males and is responsible for sex determination E. found in mitochondria but not in nuclei 2. What is the probability that on four flips of a coin, heads will occur on three flips and tails on 1? A. 1/4 B. 1/2 C. 3/16 D. 1/8 E. insufficient information to answer this question 3. A cross between two true breeding lines one with dark blue flowers and one with bright white flowers produces F1 offspring that are light blue. When the F1 progeny are selfed a 1:2:1 ratio of dark blue to light blue to white flowers is observed. What genetic phenomenon is consistent with these results? a. epistasis b. incomplete dominance c. codominance d. inbreeding depression e. random mating 4. In dihybrid crosses, the ratio 9:3:3:1 indicates. A. Codominance B. Independent assortment C. Intermediate dominance D. Three alleles for each trait 5. In a cross of a round hybrid pea with a true breeding round parent (Ww x WW), what genotypic proportions would be observed in the offspring? A. Half heterozygous, half homozygous dominant B. Half round, half wrinkled C. All heterozygous D. All round

2 6. What would be the frequency of AABBCC individuals from a mating of two AaBbCc individuals? a.. 1/64 b. 1/32 c. 1/16 d. 1/8 e. 3/16 f. 1/4 7. Probabilities are calculated using the sum rule when they. A. Are equally likely B. Are independent C. Are mutually exclusive D. Occur disproportionately 8. The genetic material DNA consists of basic subunits called A) centrioles. B) mitochondria. C) nucleotides. D) lysosomes. E) none of the above 9. A gene showing codominance a. has both alleles independently expressed in the heterozygote b. has one allele dominant to the other c. has alleles tightly linked on the same chromosome d. has alleles expressed at the same time in development e. has alleles that are recessive to each other 10. The phenomenon of independent assortment refers to: a. expression at the same stage of development b. transmission of two or more unlinked genes to the next generation c. association of an RNA and a protein implying related function d. independent location of genes from each other in an interphase cell e. association of a protein and a DNA sequence implying related function 11. If the liver cells of an animal have 24 chromosomes, its sperm cells would have how many chromosomes? A) 12 B) 6 C) 48 D) 24

3 12. The sequence of one strand of DNA is 5 TCGATC 3. The sequence of the complementary strand would be. Note polarity! A. 5 AGCTAG 3 B. 5 TCGATC 3 C. 5 CTAGCT 3 D. 5 GCTAGC 3 E. 5 GATCGA Starting with a cross between AA and aa, the proportion of heterozygotes in the F2 progeny will be? A. 1/8 B. 1/4 C. 1/3 D. 1/2 E. All heterozygotes 14. The basic structure of a nucleotide includes the following components: A) base, sugar, and phosphate. B) phosphorus and sulfur. C) mrna, rrna, and trna. D) tryptophan and leucine. E) amino acids. 15. Albinism, lack of pigmentation in humans, results from an autosomal recessive gene designated a. Two parents with normal pigmentation have an albino child. What is the probability that their next child will be albino? What is the probability that the next child will be an albino girl? A. 1/2; 1/4 B. 1/4; 1/2 C. 1/4; 1/8 D. 1/8; 1/4 16. Starting with a P generation with the following genotypes (AABB x aabb). Based on classical Mendelian inheritance, what is the expected phenotypic ratio observed among the F2 progeny? A. 9:3:3:1 B. 1:2:1 C. 3:1 D. 1:1 E. 1:1:1:1

4 17. In the previous question, if A = plain fur and a = spotted fur and B = Long ears and b = short ears, what phenotypic class would be observed in the highest proportion in the F2 generation? A. spotted - short ears B. plain - short ears C. spotted - long ears D. plain - long ears 18. A species of mice can have gray or black fur and long or short tails. A cross between pure breeding black-furred, long-tailed mice and gray-furred, short-tailed mice produce all black-furred, long-tailed offspring. Using the gene symbols G for black, g for gray, S for long and s for short, what would be the genotype of a gray-furred, short-tailed mouse? A. GGSS B. ggss C. ggss D. GgSs E. Ggss 19. Referring to question 18, how many different gametes will the black-furred, long-tailed P1 mice produce? A. 1 B. 2 C. 4 D Referring to question 18, how many different gametes do the black-furred, long-tailed F1 mice produce? A. 1 B. 2 C. 4 D A sex linked recessive alelle c produces red-green color blindness in humans. A normal woman whose father was color bind marries a color blind man. What is the probability that their first child will be a color blind boy and the second child will be a girl with normal vision? a) 1/16 b) 1/8 c) 1/4 d) 1 e) 0

5 22. X-chromosome inactivation a. normally takes place in males but not females b. is the cause of the Y chromosome being genetically inactive c. takes place in humans so that the same X chromosome is inactive in all of the cells of a female d. occurs in fruit flies but not in mammals e. results in genetically turning off one of the two X chromosomes in female mammals 23. How many different gametes can be formed by the following parental genotype? Aa BB cc DD A) 2 B) 4 C) 6 D) 8 E) In a F1 dihybrid cross (WwGg X WwGg) where W = round, w = wrinkled, G = yellow and g = green, what is the probability of obtaining an individual that is wrinkled and yellow? A. 1/16 B. 1/2 C. 9/16 D. 3/16 E. 1/4 25. Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring. 6) When the albino was crossed with a second black one, 4 black and 3 albino offspring were produced. What genetic explanation would apply to these data? A) Albino and black = codominant B) Albino = dominant; black = incompletely dominant. C) Albino = recessive; black = recessive D) Albino = recessive; black = dominant.. E) none of the above 26. Barney and Betty are about to have their first child. They both have "normal" feet but Barney's father has flat feet and Betty has a child from a previous marriage who has flat feet. Assuming flat feet is a recessive trait what is the probability that they will have a boy with flat feet? A. 1/2 B. 1/4 C. 1/8 D. 3/4 E. 3/8

6 27. In the previous question, Barney and Betty learn that they will actually have twins - dizygotic twins (from two eggs). What is the probability that they will have both a boy and a girl, both of whom are flat footed? A. 1/4 B. 1/8 C. 1/16 D. 1/32 E. 1/ A couple has four children. What is the probability that they would have four boys? A) 1/8 B) 1/16 C) 1/2 D) 1/32 E) 1/4 29. The following pedigree concerns the autosomal recessive disease phenylketonuria (PKU). The couple marked A and B are contemplating having a baby but are concerned about the baby's having PKU. What is the probability of the first child having PKU? Unless you have evidence to the contrary, assume that a person marrying into the pedigree (i.e. not a descendant of the two parents at the top of the pedigree) is not a carrier. The filled-in individuals have PKU. A) 0 B) 1/12 C) 1/4 D) 3/4 E) 9/64

7 30. Assuming the first child in question #29 has PKU what is the chance that their second child will have PKU? A) 0 B) 1/12 C) 1/4 D) 3/4 E) 9/ A selfed monohybrid characteristically produces progeny phenotypes in the ratio A) 1:1 B) 1:2:1 C) 3:1 D) 9:3:3:1 E) 1:1:1:1 32. In DNA, thymine always pairs with A) adenine B) cytosine C) guanine D) thymine E) uracil 33. If a normal man marries a woman who is a carrier for a sex-linked recessive trait, where might one expect to see the trait expressed in their children? A) In all the children B) In none of the children C) In all the sons D) In half the sons E) In half the daughters Questions refer to the following scenario: A man with type A blood marries a woman with type A blood. Their first child has type O blood. 34. What is the genotype of the MAN? A) AA B) I A i C) ii D) A E) I A I A

8 35. What proportion of his gametes are expected to contain the I A allele? A).25 B) 0 C) 1.00 D).50 E) 75% 36. What is the probability that their next child will have type A blood? A).50 B).25 C) 0 D).75 E) Pleiotropy is: A) When a single locus affects many different traits. B) When the X chromosome is inactivated in some tissues, but not others C) When one gene locus affects the expression of others D) The inheritance pattern exhibited when a gene is carried on the sex chromosome E) None of the above. 38. If genes assort independently, a selfed dihybrid characteristically produces progeny phenotypes in the ratio A) 1:1 B) 1:2:1 C) 3:1 D) 9:3:3:1 E) 1:1:1:1 39. In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female? A) 1:1 male to female B) 3:1 male to female C) 4:3 male to female D) 1:2 male to female E) 2:1 male to female

9 40. RNA differs from DNA in that RNA A) contains ribose as its sugar. B) is found only in cytoplasm. C) contains uracil instead of thymine. D) Both A and C are correct. E) A, B, and C are correct. 41. What is the primary transcript of eukaryotic genes? A) DNA B) mrna C) rrna D) hnrna E) trna 42. A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates A) the mistakes made by Mendel. B) a dihybrid cross. C) true-breeding. D) dominance. E) the blending model of genetics. 43. A couple who are both carriers of the gene for cystic fibrosis have two children who have cystic fibrosis. What is the probability that their next child will have cystic fibrosis? A) 0% B) 25% C) 100% D) 50% E) 75% 44. In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. When two roan cattle are crossed, the phenotypes of the progeny are found to be in the ratio of 1 red:2 roan:1 white. Which of the following crosses could produce the highest percentage of roan cattle? A) white x roan B) red x roan C) roan x roan D) red x white E) All of the above crosses would give the same percentage of roan.

10 45. Although the law of independent assortment is generally applicable, when two loci are on the same chromosome, the phenotypes of the offspring sometimes do not fit the phenotypes predicted. This is due to: A) linkage. B) chromosome exchange. C) translation. D) chromatid abnormalities. E) inversions. 46) Explain exactly why a change in temperature might cause an enzyme to quit functioning? a) It causes the peptide bonds in the protein to break b) It causes the nucleotide to change shape c) It causes a change of the protein confirmation at the active site d) It causes the phospholipids to denature e) None of the above 47) Which protein class directly controls many of the metabolic reactions within a cell? A) enzymes B) hydrophilic proteins C) operator proteins D) structural proteins E) repressor proteins 48) Considering the structure of double-stranded DNA, what kinds of bonds hold one complementary strand to the other A) ionic B) hydrogen C) covalent D) van der Waals E) hydrophobic and hydrophilic

11 49. A cross is made between an arginine-requiring (arg) mutant of Neurospora and wild type (+). What proportion of the progeny will require arginine? (Note: neurospora is a fungi) A) All B) None C) 1/4 D) 1/2 E) 3/4 50. The following pedigree shows the inheritance of attached earlobes (black symbols) and unattached earlobes (white symbol). Both alternative phenotypes are quite common in human populations. If the phenotypes are determined by alleles of one gene, then attached earlobes are inherited as an A) Autosomal dominant B) Autosomal recessive C) X-linked dominant D) X-linked recessive E) Could be more than one of the above