Exam 3 practice

• One of the key differences between meiosis and mitosis is a. there is only 1 round of DNA replication before mitosis, but 2 rounds of replication before meiosis. b. cells divide once in mitosis, but twice in meiosis. c. homologous chromosomes pair up in mitosis, but not in meiosis. d. A & B e. All of the above

• Meiosis II is also referred to as the equational division. This is due to a. crossing over. b. pairing of homologs. c. separation of chromatids. d. separation of homologs. e. None of the above

• In a haploid organism, most mitosis occurs a. after fertilization and before meiosis. b. after meiosis and before fertilization. c. between meiosis I and II. d. during G1. e. in diploid cells.

• Diploid cells of the fruit fly Drosophila have eight chromosomes. How many chromosomes does a Drosophila gamete have? a. 1 b. 2 c. 4 d. 8 e. 16

• Accidents during meiosis that can result in trisomies and monosomies are called a. nondisjunctions. b. inversions. c. reciprocal translocations. d. recombinations. e. acrocentricities.

• The site on the chromosome occupied by a gene is called a(n) a. allele. b. region. c. locus. d. type. e. phenotype.

• Mendel’s conclusion that individuals consist of two “factors” and pass on only one of those factors to the next generation is the basis for a. the law of segregation. b. the law of independent assortment. c. the law of dominance. d. the law of linkage. e. I fought the law and the law won.

• Which of the following methods was not used by Mendel in his study of the genetics of the garden pea? a. Maintenance of true-breeding lines b. Cross-pollination c. Microscopy d. Production of hybrid plants e. Quantitative analysis of results

• Which of the following is a possible gamete for an individual with the genotype PPrr? a. PP b. Pr c. pr d. rr e. Rp

For questions 12-14, refer to the schmoos. Two different groups of imaginary schmoos live in geographically separated locations and rarely interbreed. On one occasion, a big-footed white schmoo does mate with a small-footed brown schmoo. Three offspring result: one big-footed brown schmoo and two small-footed brown schmoos. • Which statement about the inheritance of color in schmoos is most likely to be correct? a. Brown is dominant to white b. White is dominant to brown c. White and brown are codominant d. A & C e. This cannot be answered without more information • Which statement about the inheritance of footedness in schmoos is most likely to be correct? a. Big is dominant to small b. Small is dominant to big c. Big and small are codominant d. A & C e. This cannot be answered without more information • If big feet (B) in schmoos is dominant to small feet (b), the genotype of the big-footed white parent schmoo with respect to the foot gene can a. only be bb. b. only be BB. c. only be Bb. d. either be bb or BB. e. either be bb or Bb.

• Classical albinism results from a recessive allele. Which of the following is the expected ratio for the progeny when a normally pigmented male with an albino father has children with an albino woman? a. ¾ normal; ¼ albino b. ¾ albino; ¼ normal c. ½ normal; ½ albino d. All normal e. All albino

• Mendel performed a cross between individuals heterozygous for three different traits: yellow versus green seeds (yellow is dominant), red versus white flowers (red is dominant), and green versus yellow pods (green is dominant). What fraction of the offspring would have been expected to have yellow seeds, red flowers, and yellow pods? a. 27/64 b. 12/64 c. 9/64 d. 6/64 e. 3/64

• The ABO blood groups in humans are determined by a multiple allelic system in which IA and IB are codominant and are dominant to iO. If an infant born to a type O mother also is type O, possible phenotypes for the father are a. O or A. b. A or O. c. O only. d. O, A, or B. e. impossible to determine.

• Epistasis refers to a. a group of genes that are close together. b. the equal interaction of two genes so that a new phenotype is produced. c. the expression of two genes in the same individual. d. the linear order of genes on a chromosome. e. the expression of one gene masking the expression of another.

• If 3 unlinked genes control a trait and an individual is heterozygous for 2 genes and homozygous for 1 gene, how many different gametes are possible? a. 3 b. 4 c. 6 d. 8 e. 12

• White coat color in mice is caused by an allele recessive to the dark allele for dark coat color. Twenty-four mice resulting from a cross between individuals heterozygous for this gene would be a. 6 dark; 18 white b. 18 dark; 6 white c. 12 dark; 12 white d. All dark e. All white

• Sex in humans is determined by a. a gene called SRY found on the Y chromosome. b. a gene called SRY found on the X chromosome. c. the ratio of sex determinants found on the autosomes versus the sex determinants found on the Y chromosome. d. the ratio of sex determinant found on the autosomes versus the sex determinants found on the X chromosome. e. the simple presence or absence of the Y chromosome.

• When reciprocal crosses produce identical results, the trait is a. sex-linked. b. not sex-linked. c. not autosomally inherited. d. A & C e. B & C

• In Netherlands dwarf rabbits, a gene with two alleles showing incomplete dominance produces three outcomes. Rabbits that are homozygous for one allele are small; individuals that are homozygous for the other allele die during development; individuals that are heterozygous are dwarf. If two dwarf rabbits are mated, what proportion of their surviving offspring are likely to be dwarf? a. 1/4 b. 1/3 c. 1/2 d. 2/3 e. All

• In humans, spotted teeth are caused by a dominant sex-linked gene. A man with spotted teeth whose father had normal teeth marries a woman with normal teeth. Therefore, a. all of their daughters will have normal teeth. b. all of their daughters will have spotted teeth. c. all of their children will have spotted teeth. d. half of their sons will have spotted teeth. e. all of their sons will have spotted teeth.

• A person’s genotype is AaBb for two genes linked on the same chromosome. If the two dominant alleles are on one chromosome and the two recessive alleles are on the other homologous chromosome, which of the following statements is true? a. Gametes AB, Ab, aB, and ab will be produced at an equal frequency. b. Gametes AB and ab will be produced at a higher frequency than Ab and aB. c. Gametes Ab and aB will be produced at a higher frequency than AB and ab. d. Gametes AB and ab are the only possible gametes. e. None of the above

• If the distribution of a character in a population is continuous, (ie. a bell shaped curve occurs when degree of trait is plotted against frequency) you would assume that the character is a. not controlled by genes. b. controlled by more than one gene. c. controlled by multiple alleles of the same gene. d. is heavily influenced by the environment. e. None of the above

• How does X chromosome inactivation contribute to genetic diversity? a. It controls the number and kind of genes expressed on an X chromosome. b. It determines which X chromosome is expressed in a male. c. It allows for expression of either the maternal or paternal X chromosome in different cells. d. It enhances expression of Y-linked genes in males. e. It allows the enhancement of transcription of genes on the X chromosome in males.

• The adaptor molecule used by the cell to decode the nucleotide information of mRNA and convert it to protein information is a. tRNA. b. a promoter. c. RNA polymerase. d. DNA polymerase. e. an amino acid.