Test Bank for An Introduction to Genetic Analysis Eleventh Edition Anthony JF Griffiths

Chapter 2 Single-Gene Inheritance MULTIPLE-CHOICE QUESTIONS Sections 2.1. and 2.2. (Single gene inheritance, The chromosomal basis of single-gene inheritance patterns) 1. If a plant of genotype A/a is selfed, and numerous offspring are scored, what proportion of the progeny is expected to have homozygous genotypes? A) 0 B) 25% C) 50% D) 75% E) 100% Answer: C 2. What is the maximum number of heterozygous genotypes that could be produced by monohybrid self? A) 1 B) 2 C) 3 D) 4 E) 6 Answer: A 3. A plant is heterozygous at three loci. How many different gamete genotypes can it theoretically produce with respect to these three loci? A) 2 B) 3 C) 4 D) 8 E) 16 Answer: D 4. In mountain rabbits, the EL-1 gene is located on chromosome 3. Four alleles of this gene have been identified in the population. With respect to EL-1, what is the maximum number of genotypes in the progeny of a single cross between two mountain rabbits? A) 1 B) 2 C) 3 D) 4 E) 6 Answer: D 5. A wild-type strain of haploid yeast is crossed to a mutant strain with phenotype d. What phenotypic ratios will be observed in the progeny? A) all wild type B) 75% wild type and 25% mutant (d) C) 50% wild type and 50% mutant (d) D) 25% wild type and 75% mutant (d) E) all mutant (d) Answer: C Section 2.3. (The molecular basis of Mendelian inheritance patterns) 6. Mice (Mus musculus) have 40 chromosomes per diploid cell (2n = 40). How many double- stranded DNA molecules and how many chromosomes are there in a mouse cell that is in the G2 stage of the cell cycle? A) 40 DNA molecules and 20 chromosomes B) 40 DNA molecules and 40 chromosomes C) 40 DNA molecules and 80 chromosomes D) 80 DNA molecules and 40 chromosomes E) 80 DNA molecules and 80 chromosomes Answer: D 7. A mutation occurs in a germ cell of a pure-breeding, wild-type male mouse prior to DNA replication. The mutation is not corrected, and the cell undergoes DNA replication and a normal meiosis producing four gametes. How many of these gametes will carry the mutation? A) 1 B) 2 C) 3 D) 4 E) It is impossible to predict. Answer: B 8. What is the mechanism that ensures Mendel’s first law of segregation? A) formation of chiasmata B) formation of the kinetochore C) pairing of homologous chromosomes D) segregation of homologous chromosomes during meiosis I E) segregation of sister chromatids during meiosis II Answer: D 9. A laboratory mouse homozygous for an RFLP marker is mated to a wild mouse that is heterozygous for that marker. One of the heterozygous individuals resulting from this cross is mated back to the wild parent. What proportion of the offspring will have the same RFLP pattern as the original laboratory mouse? A) none of the offspring B) 1/4 C) 1/2 D) 3/4 E) all of the offspring Answer: C 10. The diagram below shows a part of the biochemical pathway responsible for fruit color in peppers (Caspicum annuum). Enzyme 1 is responsible for catalyzing the reaction that turns the colorless precursor into yellow pigment, whereas Enzyme 2 catalyzes the step that turns the yellow pigment into red pigment. A breeder crosses a pure-breeding plant that makes yellow peppers to a pure-breeding plant that makes red peppers. What proportion of the offspring will make red peppers? Enzyme 1 Enzyme 2 Colorless precursor Yellow pigment Red pigment A) all of the offspring B) 3/4 C) 1/2 D) 1/4 E) none of the offspring Answer: A 11. The wild-type eye color in the fruit fly Drosophila melanogaster is dark red, as a result of a mixture of bright red and brown pigments. “Enzyme A” is encoded by the “a” gene, and is required to synthesize the bright red pigment. A lack of red pigment results in a somewhat brown eye color. You cross two fruit flies who are heterozygous for a recessive mutation that completely inactivates the “a” gene. What proportion of their offspring will have a recessive eye color phenotype? A) all of the offspring B) 3/4 C) 1/2 D) 1/4 E) none of the offspring Answer: D