Concept explainers
HOW DO WE KNOW?
Population geneticists study changes in the nature and amount of
(a) How do we know how much genetic variation is in a population?
(b) How do geneticists detect the presence of genetic variation as different alleles in a population?
(c) How do we know whether the genetic structure of a population is static or dynamic?
(d) How do we know when populations have diverged to the point that they form two different species?
(e) How do we know the age of the last common ancestor shared by two species?
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Essentials of Genetics (9th Edition) - Standalone book
- The groups we recognize as different human races represented populations that have been genetically isolated for a long time, we would expect to see: Select all that apply and briefly justify your answer. a) high levels of genetic variation between groups relative to what we see within groups. b) high levels of genetic variation within groups relative to what we see between groups. c) no clear pattern of genetic variation―in some regions, we would see more variation within than among groups, and in some regions we would see the opposite. d) a correlation between the amount of genetic variation between groups and the length of time the groups have been isolated from one another.arrow_forwardLet’s assume that the marbles are species of praying mantises and that the new environment consists of greenery and many bright red and white flowers a) Which colors in the genetic drift population would have better fitness in this new environment? Why/how? b) Which of the colors would have less fitness? Why/how? c) What would you expect to happen to the allele frequency for the following forms of the gene: -Green -Yellow -Red -Blue -Orangearrow_forwardNieman-Pick Syndrome involves a defective enzyme, sphyngomylinase. It is usually fatal before the age of 3. The defective allele frequency is 0.01 in Ashkenazi populations. Let’s call the healthy allele A, and the lethal allele a. a) What is the frequency of allele A? Assuming Hardy-Weinberg equilibrium, how many people do you expect to have the three genotypes in a population of 10,000? b) AA:_______ c) Aa:________ d) aa:_________arrow_forward
- You are studying an autosome trait. There are two alleles, one showing complete dominance over the other. In a population, 84% of the individuals show the dominant phenotype. Assuming that this population is under Hardy-Weinberg equilibrium, which of the following statement is TRUE? 36% of individuals have the homozygous dominant genotype. 40% of the alleles in the population is recessive. 16% of the alleles in the population is recessive. 60% of individuals have the dominant alleles.arrow_forwardwhat is the meaning of fitness ?what two things do you suppose govern the rate of evolution by natural selection?arrow_forwardPINE TREE NEEDLES Variation among members of a population can lead to natural selection, but only if two conditions are met: First, the trait must be relevant to an individual's survival and/or reproductive rate. Second, variation in this trait must be heritable, that is, at least partly controlled by genes. a. How might you design an experiment to determine the importance of needle length in determining survival and reproduction? b. How might you test the extent to which needle length is heritable?arrow_forward
- background: Lizards often have bright coloration and in some species there is variation in coloration within populations. For the sake of simplicity, let’s assume that color is genetically determined by a single gene with two alleles that interact in a codominant fashion: r+r+ = red, r+r- = yellow, r-r- = white. Imagine there is a large population of these lizards where 1 in 200 lizards have the white coloration, 30 are yellow and the rest are red. A tsunami sweeps through the population! Although no lizards died, 10 random lizards were swept to a nearby island. One of these individuals is white while the rest were yellow. Over time, these individuals remain stuck on the island and form a new population. Eventually, 80% of this population has the white coloration. Assume that color does not affect fitness in either population. question: At the time of the founding of the smaller population, (when 1/10 were white, the rest yellow), what was the chance of fixation of the r- allele via…arrow_forwardA population consist of 7 mice. For the coat trait, there are only two alleles: brown B and white (b). BB and Bb mice are brown; bb mice are white. In the population's gene pool, there are 7 white alleles(b). a) what is the frequency of the brown allel in the population? b) what do you predict the frequency of the bb genotype will be in the next generation if no evolution takes place in the population?arrow_forwardThe genetic composition of a population is 40 homozygous dominant (RR), 360 heterozygotes (Rr) and 600 homozygous recessive (rr). What is the observed frequency of the homozygous dominant individuals? [ Select] What is the observed frequency of the "r" allele? [ Select ] What is the expected frequency of the heterozygous genotype? [ Select ] If the Chi-squared value for this system is 2.40, is the population in Hardy-Weinberg equilibrium? Why? (note: the critical values for this test is 3.84), [Select ]arrow_forward
- The agouti gene determines coat colour in mice. Heterozygous mice have yellow coats, while homozygous dominant mice have black coats. However, having two copies of the recessive alleles is lethal. In a population of 2 000 mice, 1 082 mice have black coats. a) Calculate the frequency of each allele. Show all your work and express your answer as a value between 0 and 1 rounded to two decimal places. b) What percentage of the mouse population is expected to be carriers of the lethal allele? Show all your work and express your answer rounded to one decimal place. c) How many mice will die during fetal development? Show all your work and round your answer to the closest whole number.arrow_forwardPolydactyly (being born with more than 5 fingers or toes) is caused by a dominant allele of a single gene. If the frequency of the recessive allele is 0.9 (or 90%) in a certain population, what percentage of the population would you expect to be heterozygotes? Assume this population is in Hardy-Weinberg equilibrium. Note: In reality, there are other causes of polydactyly when it is accompanied by other disorders, so this problem is an over-simplification. 18% 1% 90% 81%arrow_forwardA population consists of 7 mice. For the coat color trait, there are only two alleles: brown (B) and white (b). BB and Bb mice are brown; bb mice are white. In the population's gene pool, there are 7 white alleles (b). a) What is the frequency of the brown allele in the population? Select) b) What do you predict the frequency of the bb genotype will be in the next generation if no evolution takes place in the population? I Select | c) The mice live on dark black, volcanic rocks in the Arizona desert and two hawks are introduced into the area as part of wildlife rehabilitation program. You sample the mouse population after the hawk reintroduction and find the following numbers: 24 BB mice, 52 Bb mice, 24 bb mice. Has natural selection by the hawks caused the population to evolve significantly? I Select]arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning