Chapter 3 Mendelian Genetics1) Which of the following groups of scientists were influential around the year 1900 in setting the stage for our present understanding of transmission genetics?A) Beadle, Tatum, LederbergB) Watson, Crick, Wilkins, FranklinC) deVries, Correns, Tschermak, Sutton, BoveriD) Darwin, Mendel, LamarckE) Hippocrates, Aristotle, KolreuterAnswer: CSection: 3.52) Name the single individual whose work in the mid-1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With what organism did this person work?A) Gregor Mendel; Pisum sativumB) George Beadle; NeurosporaC) Thomas Hunt Morgan; DrosophilaD) Calvin Bridges; DrosophilaE) Boris Ephrussi; EphestiaAnswer: ASection: Introduction3) A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?A) 25%B) 50%C) about 66%D) 75%E) about 90%Answer: DSection: 3.24) Polydactyly is expressed when an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly?A) 1/32B) 1/8C) 7/16D) 1/2E) 3/4Answer: DSection: 3.21Copyright © 2012 Pearson Education, Inc.5) Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what percentage of their offspring would be expected to have straight hair?A) 25% curlyB) 50% straightC) 75% curlyD) 100% straightE) It is impossible to predict the outcome.Answer: BSection: 3.26) Which types of phenotypic ratios are likely to occur in crosses when dealing with a single gene pair for which all the genotypic combinations are of equal viability?A) 9:3:3:1, 27:9:9:9:3:3:3:1B) 1:2:1, 3:1C) 1:4:6:4:1, 1:1:1:1D) 12:3:1, 9:7E) 2:3, 1:2Answer: BSection: 3.27) Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring. When the albino was crossed with a second black guinea pig, 4 black and 3 albino offspring wereproduced. What genetic explanation would apply to these data?A) albino = recessive; black = recessiveB) albino = dominant; black = incompletely dominantC) albino and black = codominantD) albino = recessive; black = dominantE) None of the answers listed is correct.Answer: DSection: 3.28) The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus would be called ________.A) segregationB) independent assortmentC) continuous variationD) discontinuous variationE) dominance or recessivenessAnswer: ASection: 3.22Copyright © 2012 Pearson Education, Inc.9) The Chi-square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as ________.A) the number of categories being comparedB) one less than the number of classes being comparedC) one more than the number of classes being comparedD) ten minus the sum of the two categoriesE) the sum of the two categoriesAnswer: BSection: 3.810) Assume that in a series of experiments, plants with round seeds were crossed with plants with wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled.a) What is the most probable genotype of each parent?(b) What genotypic and phenotypic ratios are expected?(c) Based on the information provided in part (b), what are the expected (theoretical) numbers of progeny (400 total) of each phenotypic class?Answer: (a) assuming that round (W) is dominant to wrinkled (w): Ww × ww(b) 1:1(c) 200Section: 3.211) In peas, gray seed color is dominant to white. For the purposes of this question, assume that Mendel crossed plants with gray seeds with each other and the following progeny were produced: 320 gray and 80 white.(a) What is the most probable genotype of each parent?(b) What genotypic and phenotypic ratios are expected in the progeny of such a cross?Answer: (a) assuming the following symbols: G = gray and g = white, Gg × Gg(b) genotypic = 1:2:1, phenotypic = 3:1Section: 3.23Copyright © 2012 Pearson Education, Inc.12) Assume that you have a garden and some pea plants have solid leaves and others have stripedleaves. You conduct a series of crosses [(a) through (e)] and obtain the results given in the table.Cross Progeny solid striped(a) solid × striped 55 60(b) solid × solid 36 0(c) striped × striped 0 65(d) solid × solid 92 30(e) solid × striped 44 0Define gene symbols and give the possible genotypes of the parents of each cross.Answer: (a) From cross (d), assume that solid (S) is dominant to striped (s): Ss × ss.(b) SS × SS or SS × Ss(c) ss × ss(d) Ss × Ss(e) SS × ssSection: 3.213) The phenotype of vestigial (short) wings (vg) in Drosophila melanogaster is caused by a recessive mutant gene that independently assorts with a recessive gene for hairy (h) body. Assume that a cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and normal body hair. The wild-type F1 flies were crossed among each other to produce 1024 offspring. Which phenotypes would you expect among the 1024 offspring, and how many of each phenotype would you expect?Answer: Phenotypes: wild, vestigial, hairy, vestigial hairyNumbers expected: wild (576), vestigial (192), hairy (192), vestigial hairy (64)Section: 3.314) Two organisms, AABBCCDDEE and aabbccddee, are mated to produce an F1 that is self-fertilized. If the capital letters represent dominant, independently assorting alleles:(a) How many different genotypes will occur in the F2?(b) What proportion of the F2 genotypes will be recessive for all five loci?(c) Would you change your answers to (a) and/or (b) if the initial cross occurred between AAbbCCddee × aaBBccDDEE parents?(d) Would you change your answers to (a) and/or (b) if the initial cross occurred between AABBCCDDEE × aabbccddEE parents?Answer: (a) 35 = 243(b) 1/243(c) no(d) yesSection: 3.415) How many different kinds of gametes can be produced by an individual with the genotype 4Copyright © 2012 Pearson Education,