Chapter 23

12 September 2022
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question
Which of these individuals is a homozygous genotype?
answer
AA
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All the genes in a population are that population's_____.
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gene pool
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Genetic drift is a process based on _____.
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the role of chance
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A mutation occurs when _____.
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there is a change in the DNA sequence of a gene
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Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population?
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Alleles that promote "tallness" will decrease in frequency.
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Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.
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genetic drift
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The ease with which humans travel across the globe is likely to increase _____.
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gene flow
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Homologous pairs of chromosomes are lined up independently of other such pairs during _____.
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metaphase I
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Crossing over, resulting in an increase in genetic variation, occurs between _____.
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nonsister chromatids of homologous chromosomes
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In human gamete production there is an average of _____ crossover events per chromosome pair.
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2-3
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Which of these gametes contain one or more recombinant chromosomes?
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B,C,F, and G
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This animation illustrates _____ as it occurs during _____.
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crossing over.... prophase I
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The original source of all genetic variation is _____.
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mutation
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Which of the following are basic components of the Hardy-Weinberg model?
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Frequencies of two alleles in a gene pool before and after many random matings
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Which of the following statements is not a part of the Hardy-Weinberg principle?
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The genotype frequencies in the offspring generation must add up to two.
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True or false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.
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True
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What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?
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0.4
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What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?
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The frequency of the A1 allele is 0.3.
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Which of the following evolutionary forces results in adaptive changes in allele frequencies?
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Selection
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What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene?
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The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively.
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Which of the following evolutionary forces could create new genetic information in a population?
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Mutation
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According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.
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sexual reproduction
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What process is illustrated by this animation?
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gene flow
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What process is illustrated by this animation?
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natural selection
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Generation-to-generation change in the allele frequencies in a population is _____.
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microevolution
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The evolutionary effects of genetic drift are greatest when _____.
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the population size is small
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Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____.
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directional selection
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What is the only evolutionary mechanism that consistently leads to adaptive evolution?
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natural selection
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No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is
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the reshuffling of alleles in sexual reproduction
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Which statement correctly describes the role of chance in evolution?
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The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA.