Genetics - Problem Drill 24: Evolutionary Genetics No. 1 of 10 1. A phylogenetic tree gives all of the following information except for. (A) DNA sequence homology among species. (B) Protein sequence similarity among species. (C) Morphological similarity among species. (D) Evolutionary relationships among species. (E) Genetic distance among species. A phylogenetic tree gives information about DNA sequence homology among species. The more homology they share, the less distance there is on a tree. A phylogenetic tree also implies protein sequence similarity among species, which is the same as DNA sequence. C. Correct! A phylogenetic tree does not give information on the morphological similarity among species because morphological similarity can be from homoplasy. That is what a phylogenetic tree intends to depict. A phylogenetic tree gives information about genetic distance by giving DNA/protein homology among species. A phylogenetic tree is a direct diagram on the comparison of DNA/protein sequences among species. (C)Morphological similarity among species.
No. 2 of 10 2. Two closely-related spider species are found to live in the same area but are completely isolated reproductively. What is the most likely speciation mode for these two spiders? (A) Allopatric (B) Parapatric (C) Peripatric (D) Sympatric (E) None of the above Allopatric means speciation through geographic separation; this is not the case here. Parapatric means a continuously distributed population; this is not the case here. C. Incorrect! Peripatric means mostly geographic, a small population isolated at the edge of a larger population. D. Correct! Sympatric is most likely what happened in this case, which is due to genetic drift; geographic factors do not play a significantly role here. There is one correct answer above. There are four modes of speciation, three of which are related to geography; only sympatric occurs without geographic influence. (D)Sympatric
No. 3 of 10 3. A butterfly species has a selection against a recessive allele; due to a change in the environment, about 20% of homozygous recessive individuals die. The allele frequency for a is 0.4 before the environmental change. What will be the allele frequency for a after the population reaches equilibrium again? (A) 0.20 (B) 0.60 (C) 0.40 (D) 0.37 (E) 0.63 0.2 is the selection coefficient for a; the portion that die after selection, s. 0.6 is the allele frequency for A before selection, q. C. Incorrect! 0.4 is the allele frequency for a before selection, p. D. Correct! 0.37 is the allele frequency after selection, p. 0.63 is the allele frequency for A after selection. The allele frequency for a is p = 0.4; therefore, we know the allele frequency for A is q = 0.6. The selection coefficient s for a is s = 0.2. According to the formula, the new allele frequency for a is p = p/(1-sq 2 ) = 0.4/ (1-0.2*0.6 2 ) = 0.37. From this, we know the allele frequency for A will be 1 0.37 = 0.63. (D)0.37
No. 4 of 10 4. Assume an insect species has selection against both homozygous AA and aa. 10% of the AA genotype will not have offspring and 15% of the aa genotype cannot survive. What will be the allele frequency of A after the population reaches equilibrium? (A) 0.9 (B) 0.8 (C) 0.4 (D) 0.2 (E) 0.5 There is no way to arrive at 0.9 as the answer. p* = s/(s+t) = 0.1/(0.1+0.15) = 0.4. 0.8 doubled the rate. C. Correct! p* = s/(s+t) = 0.1/(0.1+0.15) = 0.4. This is only half of the calculated rate. There is no way to arrive at 0.5 as the answer. This is a typical heterozygote superiority problem. The selection coefficient for AA is s = 0.1, for aa t = 0.15. Although the initial allele frequency is unknown, the allele frequency of A can be calculated by formula p* = s/(s+t) = 0.1/(0.1+0.15) = 0.4. (C)0.4
No. 5 of 10 5. Synonymous substitution rate is usually greater than non-synonymous substitution; the reason is. (A) All non-synonymous substitutions are deleterious to the organisms. (B) The rate of non-synonymous substitution equals the rate of mutation. (C) The synonymous substitution does not change the amino acid sequence; therefore, they usually do not affect the protein function. (D) The synonymous substitutions are more useful than non-synonymous substitution. (E) The non-synonymous substitution occurs outside of the coding sequence. Not all non-synonymous substitution is deleterious; some may be favorable in certain environments. The rate of non-synonymous substitution does not equal the rate of mutation. C. Correct! Synonymous substitution has another name; it is also called a silent mutation. These do not change amino acid sequence and do not affect protein function in general. There is no comparison in terms of use for synonymous substitutions and nonsynonymous substitution. The non-synonymous substitution occurs within a coding sequence. Change in nucleotide sequence is an important force for evolution. (C)The synonymous substitution does not change the amino acid sequence; therefore, they usually do not affect the protein function.
No. 6 of 10 6. What are the driving forces of evolution (choose the best answer)? (A) Natural selection and stability of an organism s genome. (B) Mutation, natural selection and migration. (C) Mutation, natural selection, genetic drift and migration. (D) Evolution has only one driving force, migration. (E) The driving forces for evolution include migration and under-population. Genetic drift and changes in an organism s genome is one of the driving forces of evolution. Mutation, natural selection, genetic drift and migration are the driving forces of evolution. C. Correct! Mutation, natural selection, genetic drift and migration are the driving forces of evolution. Migration is one of four main driving forces, along with mutation, natural selection, and genetic drift. Under-population would cut down on the pressure and competition for resources that contributes to natural selection. There are four main driving forces in evolution: natural selection, mutation, genetic drift and migration or gene flow. (C)Mutation, natural selection, genetic drift and migration.
No. 7 of 10 7. Which of the following statements about Darwinian fitness (W) is correct? (A) Fitness (W) is defined as the relative reproductive ability of a genotype. (B) Fitness (W) is defined as the reproductive ability of the phenotype. (C) Relative fitness is the absolute number of surviving progeny of one genotype. (D) Darwinian fitness only applies to one single generation. (E) Relative fitness is the ratio between the numbers of individuals with that genotype after selection to those before selection. A. Correct! Fitness (W) is defined as the relative reproductive ability of a genotype. Fitness (W) is defined as the relative reproductive ability of a genotype. C. Incorrect! Relative fitness is the average number of surviving progeny of one genotype, compared with the average number of surviving progeny of a competing genotype after a single generation. Darwinian fitness, such as relative fitness, includes numbers of progeny from 2 generations. Absolute fitness is the ratio between the numbers of individuals with that genotype after selection to those before selection. Fitness W is defined as the relative reproductive ability of a genotype. W (fitness) is usually equal to the proportion of an individual s genes in all the genes of the next generation. Absolute fitness is the ratio between the numbers of individuals with that genotype after selection to those before selection. Relative fitness is the average number of surviving progeny of one genotype, compared with the average number of surviving progeny of a competing genotype after a single generation. (A) Fitness (W) is defined as the relative reproductive ability of a genotype.
No. 8 of 10 8. Selection coefficient. (A) (S) is related to the unchanged population. (B) (S) is a measure of natural selection. (C) Can be calculated using the following formula: S=1/W. (D) Calculations, including the term W, represent genetic wobble. (E) Is independent of the effects of generation changes. The selection coefficient (S) is a measure of natural selection. B. Correct! The selection coefficient (S) is a measure of natural selection. C. Incorrect! The selection coefficient is calculated using: S=1-W. The W represents the Darwinian fitness. Because W (fitness) is in the equation to calculate the selection coefficient, the relative changes between 2 or more generations does influence this. The selection coefficient (S) is a measure of natural selection. S ranges between 0 and 1. When S=0, the population is in Hardy-Weinberg s equilibrium. When S=1, the allele will disappear. (B)(S) is a measure of natural selection.
No. 9 of 10 9. Which of the following statements about peripatric speciation is correct? (A) When a population is split into two geographically isolated ones, this is known as peripatric speciation. (B) Peripatric speciation is when the geographic zones of two diverging populations merge. (C) Peripatric speciation is when a new species is formed in small isolated peripheral populations, which are not permitted to exchange genes with the main population. (D) During peripatric speciation, new populations exchange genes with each old population. (E) Geography plays no role in peripatric speciation. When a population is split into two geographically isolated ones, this is known as allopatric speciation. Peripatric speciation is when a new species is formed in small isolated peripheral populations, which are not permitted to exchange genes with the main population. C. Correct! Peripatric speciation is when a new species is formed in small isolated peripheral populations, which are not permitted to exchange genes with the main population. During peripatric speciation, peripheral populations are prevented from exchanging genes with the main population. Geography does play a role; the isolated population is prevented from interacting genetically with the main population. In peripatric speciation, a new species is formed in small isolated peripheral populations, which are prevented from exchanging genes with the main population. (C)Peripatric speciation is when a new species is formed in small isolated peripheral populations, which are not permitted to exchange genes with the main population.
No. 10 of 10 10. What is reinforcement in evolutionary genetics? (A) Reinforcement is the process by which natural selection increases reproductive isolation. (B) Reinforcement is the process by which natural selection decreases reproductive isolation. (C) This process takes place when two species are separated. (D) With reinforcement, if the hybrids are superior or equal, then the two species will remain separated. (E) Reinforcement stops when the reproductive isolation is incomplete. A. Correct! Reinforcement is the process by which natural selection increases reproductive isolation. Reinforcement is the process by which natural selection increases reproductive isolation. C. Incorrect! Reinforcement takes place when two species are separated and then come back together. With reinforcement, if the hybrids are superior or equal, then the two species will merge. Reinforcement stops when the reproductive isolation is complete. Reinforcement is the process by which natural selection increases reproductive isolation. Reinforcement occurs after two populations of the same species are separated and then come back into contact. If their reproductive isolation was complete, then two incompatible species exist and no further reinforcement occurs. If their separation was not complete, then they may interact. Hybrids may be infertile or fertile but less fit, in which case reinforcement takes place. (A)Reinforcement is the process by which natural selection increases reproductive isolation.