BIO 182 Exam 2 | Verified with 100% Correct Answers

BIO 182 Exam 2 | Verified with 100% Correct Answers In a simple Mendelian monohybrid cross, true-breeding tall plants are crossed with short plants, and the F1 plants, which are all tall, are allowed to self-pollinate. What fraction of the F2 generation are both tall and heterozygous? a. 1⁄8 b. 1⁄4 c. 1⁄3 d. 2⁄3 e. 1⁄2 The phenotype of an individual a. depends at least in part on the genotype. b. is either homozygous or heterozygous. c. determines the genotype. d. is the genetic constitution of the organism. e. is either monohybrid or dihybrid. The ABO blood groups in humans are determined by a multiple-allele system in which IA and IB are codominant and are both dominant to IO. A newborn infant is type A. The mother is type O. Possible phenotypes of the father are a. A, B, or AB. b. A, B, or O. c. O only. d. A or AB. e. A or O Which statement about an individual that is homozygous for an allele is not true? a. Each of its cells possesses two copies of that allele. b. Each of its gametes contains one copy of that allele. c. It is true-breeding with respect to that allele. d. Its parents were necessarily homozygous for that allele. e. It can pass that allele to its offspring. Which statement about a test cross is not true? a. It tests whether an unknown individual is homozygous or heterozygous. b. The test individual is crossed with a homozygous recessive individual. c. If the test individual is heterozygous, the progeny will have a 1:1 ratio. d. If the test individual is homozygous, the progeny will have a 3:1 ratio. e. Test cross results are consistent with Mendel's model of inheritance for unlinked genes Linked genes a. must be immediately adjacent to one another on a chromosome. b. have alleles that assort independently of one another. c. never show crossing over. d. are on the same chromosome. e. always have multiple alleles. In the F2 generation of a dihybrid cross a. four phenotypes appear in the ratio 9:3:3:1 if the loci are linked. b. four phenotypes appear in the ratio 9:3:3:1 if the loci are unlinked. c. two phenotypes appear in the ratio 3:1 if the loci are unlinked. d. three phenotypes appear in the ratio 1:2:1 if the loci are unlinked. e. two phenotypes appear in the ratio 1:1 whether or not the loci are linked. The genetic sex of a human is determined by a. ploidy, with the male being haploid. b. the Y chromosome. c. X and Y chromosomes, the male being XX. d. the number of X chromosomes, the male being XO. e. Z and W chromosomes, the male being ZZ. In epistasis a. nothing changes from generation to generation. b. one gene alters the effect of another. c. a portion of a chromosome is deleted. d. a portion of a chromosome is inverted. e. the behavior of two genes is entirely independent 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(n) _______ trait is one that can be passed from one generation to another. Heritable A(n) _______ is an observable feature, such as flower color; a(n) _______ is a particular form of a character, such as a white flower character; trait A cross between two parents that differs by a single trait is a(n) _______ cross. Monohybrid When a cross is made and a trait disappears in the F1 generation, only to reappear in the F2, the trait is probably _______. Recessive The physical appearance of a character is the _______, whereas the genetic constitution is the _______. phenotype; genotype A cross between two heterozygous parents that differs by two independent traits is a(n) _______ cross. Dihybrid To determine the overall probability of independent events, one should _______ the probabilities of the individual events. Multiply To determine the probability of an event that can occur in two or more different ways, one should _______ the individual probabilities Add Mendel's laws of inheritance can be applied to human genetics through the study of _______. Pedigrees One particular allele of a gene may be defined as _______, or standard, because it is present in most individuals and gives rise to an expected trait, or phenotype. wild type The AB phenotype found in individuals with an IAIB genotype is an example of _______. Codominance When many genes contribute to the phenotype, variation is said to be continuous, or _______. Quantitative Quantitative variation is the result of the interaction of _______ and _______. genes; environment Genes at different loci on the same chromosome can separate and recombine to form _______. recombinant chromosomes Recombination is most likely to occur between two loci that are _______. far apart Geneticists make use of _______ frequencies to create genetic maps that show the arrangement of genes on a chromosome. Recombinanation A female that is heterozygous for a recessive sex-linked trait is called a _______. carrier Long-horned cattle have greater difficulty moving through heavily forested areas compared with cattle that have short or no horns, but long-horned cattle are better able to defend their young against predators. This contrast is an example of a. an adaptation. b. genetic drift. c. natural selection. d. a trade-off. e. None of the above Which of the following is true? a. Darwin and Wallace were both influenced by Malthus. b. Wallace proposed a theory of evolution by natural selection that was similar to Darwin's. c. Malthus claimed that because human population growth would outstrip any increases in food production, famine was a likely result. d. Darwin realized that all populations had the capacity to rapidly increase in numbers. e. All of the above The phenotype of an organism is a. the type specimen of its species in a museum. b. its genetic constitution, which governs its traits. c. the chronological expression of its genes. d. the physical expression of its genotype. e. its adult form. The appropriate unit for defining and measuring genetic variation is the a. cell. b. individual. c. population. d. community. e. ecosystem. Which statement about allele frequencies is not true? a. The sum of all allele frequencies at a locus is always 1. b. If there are two alleles at a locus and we know the frequency of one of them, we can obtain the frequency of the other by subtraction. c. If an allele is missing from a population, its frequency in that population is 0. d. If two populations have the same allele frequencies at a locus, they must have the same proportion of homozygotes at that locus. e. If there is only one allele at a locus, its frequency is 1. Which of the following is not required for a population at Hardy-Weinberg equilibrium? a. There is no migration between populations. b. Natural selection is not acting on the alleles in the population. c. Mating is random. d. Multiple alleles must be present at every locus. e. All of the above The fitness of a genotype is a function of the a. average rates of survival and reproduction of individuals with that genotype. b. individuals that have the highest rates of both survival and reproduction. c. individuals that have the highest rates of survival. d. individuals that have the highest rates of reproduction. e. average reproductive rate of individuals with that genotype. Laboratory selection experiments with fruit flies have demonstrated that a. bristle number is not genetically controlled. b. bristle number is not genetically controlled, but changes in bristle number are caused by the environment in which the fly is raised. c. bristle number is genetically controlled, but there is little variation on which natural selection can act. d. bristle number is genetically controlled, but selection cannot result in flies having more bristles than any individual in the original population had. e. bristle number is genetically controlled, and selection can result in flies having more, or fewer, bristles than any individual in the original population had. Disruptive selection maintains a bimodal distribution of bill size in the West African seedcracker because a. bills of intermediate shapes are difficult to form. b. the birds' two major food sources differ markedly in size and hardness. c. males use their large bills in displays. d. migrants introduce different bill sizes into the population each year. e. older birds need larger bills than younger birds. Which of the following is not a reason why trade-offs constrain evolution? a. Most adaptations impose both fitness costs and benefits. b. Structures such a horns and antlers are metabolically costly to produce, but result in more reproduction by the males that possess them. c. Changes in allele frequencies may be influenced by chance events. d. Ability to consume toxic prey may reduce mobility. e. Adaptations can evolve only if the fitness benefits they confer exceed the costs they impose. The differential contribution of offspring to the next generation by various genetic types belonging to the original population is known as _______. natural selection A main goal of the field of _______ is to explain the origin and maintenance of genetic variation. population genetics If the frequency of one allele at a locus with two alleles is 0.73, the frequency of the other allele must be _______. 0.27 If there is only one allele at a locus in a particular population, that allele is said to be _______. Fixed Suppose that in a population of 1400, 125 individuals are homozygous for allele A7 and 450 are heterozygous for the allele. The frequency of the A7 allele would be _______. 0.25 The equation p2 + 2pq + q2 = 1 is known as the _______ equation. Hardy-Weinberg Under Hardy-Weinberg equilibrium, if the frequency of one allele is 0.7 and the frequency of the other allele is 0.3, then _______ of the population should be heterozygotes. 0.42 In small populations, the random process of _______ can cause large changes in allele frequency from one generation to the next. genetic drift The reproductive contribution of a phenotype to subsequent generations (relative to the contributions of other phenotypes) is called its _______. Fitness When _______ selection operates, individuals at opposite extremes of a character distribution contribute more offspring to the next generation than do those that are close to the mean. Disruptive A special type of natural selection called _______ acts on characters that determine mating success. sexual selection One disadvantage of sexual reproduction is that _______ breaks up adaptive combinations of genes. Recombination A clade is a. a type of phylogenetic tree. b. a group of evolutionarily related species that share a common ancestor. c. a tool for constructing phylogenetic trees. d. an extinct species. e. an ancestral species. Phylogenetic trees may be constructed for a. genes. b. species. c. major evolutionary groups. d. viruses. e. All of the above A shared derived trait, used as the basis for inferring a monophyletic group, is called a. a synapomorphy. b. a homoplasy. c. a parallel trait. d. a convergent trait. e. a phylogeny. The parsimony principle can be used to infer phylogenetic trees because a. evolution is nearly always parsimonious. b. it is logical to adopt the simplest hypothesis capable of explaining the known facts. c. once a trait changes, it never reverses condition. d. all species have an equal probability of evolving. e. closely related species are always very similar to one another. Convergent evolution and evolutionary reversal are two sources of a. homology. b. parsimony. c. synapomorphy. d. monophyly. e. homoplasy. Which of the following are commonly used to infer phylogenetic relationships among plants but not among animals? a. Nuclear genes b. Chloroplast genes c. Mitochondrial genes d. Ribosomal RNA genes e. Protein-coding genes Which of the following is not true of maximum likelihood or parsimony methods for inferring phylogeny? a. The maximum likelihood method requires an explicit model of evolutionary character change. b. The parsimony method is computationally easier than the maximum likelihood method. c. The maximum likelihood method is easier to treat in a statistical framework. d. The maximum likelihood method is most often used with molecular data. e. Parsimony is usually used to infer time on a phylogenetic tree. Taxonomists strive to include taxa in biological classifications that are a. monophyletic. b. paraphyletic. c. polyphyletic. d. homoplastic. e. monomorphic. Which of the following groups have separate sets of rules for nomenclature?