Copy of POB II Exam 1_ Practice Exam (2020)

POB II Exam I 1. Consider a trait affected by a single locus. If the heterozygotes have a phenotype that is identical to that of one of the two classes of homozygote, we call the relationship between genotype and phenotype a. Linkage b. Overdominance c. Additivity d. Partial Dominance e. Dominance 2. Mendel showed that flower position (side vs. top) and pod shape (inflated vs. constricted) each behaved as single-locus Mendelian traits, just like pea shape (round vs. wrinkled) and pea color (yellow vs. green). The flower position locus is unlinked to the pod shape locus. When Mendel crossed homozygous side-flower inflated-pod peas to homozygous top-flower constricted-pod peas, the F1s were 100% side-flower inflated-pod in phenotype. If Mendel allowed the F1s to self fertilize, what’s the expected frequency of side-flower inflated-pod plants in the F2 generation? a. 9/16. SsIi vs IiSs b. 7/16 c. 1/4 d. 3/16 e. 1/16 3. Mussels that live in streams have fish-shaped extensions of their mantle tissue. They wiggle these around and predatory fish bite them, transferring mussel larvae into the fish’s mouth. An evolutionary biologist, careful not to ascribe intention to the mussels, and avoiding teleological thinking, would say that the explanation for fish-shaped lure is that a. Mussels are trying to trick the fish into acting as couriers to transport their larvae upstream

b. The mussel’s lure is designed to trick fish. c. The fish-shaped mantle tissue is the result of horizontal gene transfer from fish d. Mantle shape is heritable, and mussels whose mantle shape is more successful at attracting fish have more offspring that survive to adulthood than mussels whose mantle shape is less successful at attracting fish. e. Mussels evolved fish-shaped lure in order to attract fish so that the larvae can feed on fish blood 4. Suppose we establish an experimental population of rabbits on a deserted island. We introduce 4,000 gray rabbits and 6,000 brown ones. The starting rabbits come from established breeding stocks, and they’re all homozygous at the fur locus, the Mendelian locus that affects coat color. The gray rabbits are fur g /fur g , and the brown ones are fur b /fur b . The brown phenotype is recessive with respect to the fur locus. If coat color has no effect on mating behavior (that is, the rabbits mate randomly), and it has no effect on predation or any other aspect of rabbit fitness, what’s the expected frequency of brown rabbits in the next generation? a. 16% b. 36% c. 40% d. 48% e. 60% 5. Biologists describe an organism as having female function if it a. Has female-typical external anatomy b. Makes gametes of the large type, in a species with anisogamy c. Makes only a single class of gamete that is different in size from the single class that males make d. Has two X chromosomes in a species with X,Y sex determination, or a Z and a W in a species with Z,W sex determination e. Mates with males 6. Which modes of inheritance are compatible with this pedigree?

10. The method that uses restriction digests to genotype individuals at a SNP (ONEEE )locus works if which condition is met: a. PCR primers bind to different locations depending on the SNP alleles b. the restriction enzyme cuts the DNA from one allele but not the other c. a microarray is available that distinguishes between the two alleles by hybridization d. Sanger sequencing is cheaper than next-generation sequencing e. we can visualize the restriction enzyme using protein gel electrophoresis 11. Silkworms ( Bombyx mori ) are diploids with 28 pairs of chromosomes (2n = 56). A silkworm sperm cell has how many chromatids? a. 7 b. 14 c. 28 d. 56 e. 112 12. If we want to increase the heritability of a trait, which of the following approaches is most likely to work? a. Randomly distribute the organisms across a range of different environments b. Only consider genetically identical individuals c. Decrease the amount of environmental variation that affects the trait d. Decrease the overall quality of the environment that the organisms experience e. There is no way to increase the heritability of a trait 13. Two species of birds are strongly pre-zygotically isolated. Which of the following are we unlikely to observe when we see these birds in sympatry? a. Different mating behaviors in the different species b. Different habitat preferences in the different species c. Reproductive anatomy mismatch that precludes mating between the species d. Hybrids between the species e. If they are different species then they cannot be in sympatry 14. When chicken breeders select for meatier chickens, they are applying a. The Panglossian Paradigm b. Stabilizing selection c. Disruptive selection d. Directional selection

e. Frequency-dependent selection 15. The Dobzhansky-Muller model of speciation requires that a. Behavioral isolating mechanisms reduce interspecific mating attempts b. Multiple loci are involved in speciation c. Reinforcement occurs after allopatric populations return to sympatry d. Allopatry is due to dispersal e. The effect of a locus depends on the environment 16. Cycles of evolution in which a species evolves resistance to a parasite, and the parasite evolves ways to evade that resistance, and the first species evolves new forms of resistance, and so forth, illustrate the idea of a. Evolutionary spandrels b. Red Queen dynamics c. Underdominance d. Oligogeny e. Genotype-environment correlation 17. Two parents are both heterozygous for a recessive condition. If they have five children, what’s the probability that one or more of the children are affected by the disease? a. 1 - (1/4) 5 = 0.999 b. 1 - (3/4) 5 = 0.763 (since 75% kids will be dominant we do 1 - non affected ^5) c. (3/4) 5 = 0.237 d. 3 / (4) 5 = 0.003 e. (1/4) 5 = 0.00098 18. In a population with a constant population size of 1000 individuals, with random mating, no selection, and no new mutations, at a locus with two alleles, a. Allele frequencies will remain constant over time b. The dominant allele will increase in frequency c. Allele frequencies will fluctuate randomly due to genetic drift d. The change in allele frequency will depend on the heritability e. Sympatric speciation will occur

Q1: Calculate a chi-square test statistic that tells us how far these data are from the expected counts of spotted and spotless flowers under the hypothesis of Mendelian inheritance. Punnet sq - SPOTLESS IS HETEROZYGOUS S s S SS Ss s Ss ss So you expect 1/4 to be ss 1/2 to be Ss and 1/4 to be SS So you expect 3/4 of the offspring to show the spots and 1/4 to show spotless that gets you expected 19-27 ^ 2 / 27 = 64 / 27 = 2.37 Q2: With one degree of freedom, chi-square values greater than 3.84 correspond to p-values less than 0.05. What are the data telling us? (Answer in one short sentence) 2.37 > 3.84 , fail to reject null hypothesis Open-Ended Question 4 Goat breeders want to have goats with higher milk yields. The method of artificial selection is very effective for achieving this goal, and the current average annual milk yield is about 2,000 lbs for the LaMancha breed of goats, which are raised in several places, including the Welsh villages of Caefyrddin and Mwynglawdd. Using an elaborate experimental breeding design, the breeders estimate that the additive genetic variance is 10,000 lbs 2 in each location. The total phenotypic variance is 100,000 lbs 2 in Caefyrddin and 80,000 lbs 2 in Mwynglawdd. P = g + e Q1: Which location has the highest narrow-sense heritability for milk yield? Need bleeders Q2: A breeder in Mwywglandd selects female goats that produce on average 2,100 lbs per year and mates them to male goats that are expected to be similarly genetically-endowed for high milk yield (this is readily determined by measuring the average milk yield of multiple daughters of a male goat). In summary, the average milk yield of the selected class is 2,100 lbs, and the average of the whole pre-selection

population is 2,000 lbs. In the next generation, after selection, what’s the expected average milk yield of the breeder’s female goats? Open-Ended Question 5 This is a linkage problem. It may help to draw out what the chromosomes look like, so you can see which ones are parental and which ones are recombinant. Researchers studying the snail Biomphalaria glabrata wanted to learn the genetic distance between two SNP loci. They started with two parental snails. One was a C/C homozygote at locus 1 and G/G homozygote at locus 2. The other was a T/T homozygote at locus 1 and an A/A homozygote at locus 2. They generated F1 snails (all C/T heterozygotes at locus 1 and G/A heterozygotes at locus 2). Then they crossed an F1 snail to a C/C G/G double homozygote. In the progeny of that cross, they observed the following genotypes. Locus 1 Locus 2 Number of snails C/C G/G 32 T/C A/G 35 C/C A/G 16 T/C G/G 17 What is the estimated recombination frequency between Locus 1 and Locus 2? Open-Ended Question 6 Here’s a picture of the distribution of bean size in a collection of genetically identical beans. How do we explain the normal-shaped curve of bean sizes among these genetically identical individuals?