BIO 3102 Study Guide - Ring Species, Ernst Mayer, Ensatina

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peartortoise481

10 Jul 2014

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Document Summary

Evolutionary changes that result from changes in allele frequencies in a population, or in chromosome structure or numbers due to mutation and recombination. Need to look at variation within the population. Essentially the change of an allele frequency within a population. Synthetic theory of evolution: population genetics and natural selection based on. We can make predictions and calculations from frequencies in alleles. Hardy-weinberg principle: p2 + q2 + 2pq = 1. 00. Selecting against recessive genes which results in the divergence of these genes. Fitness of heterozygous is minimized and homozygous is dramatically reduced. In the end, the final gene frequency does not equal the initial gene frequency. If selection pressure is mild, the frequency of the genes in the population rarely changes over the generations. If selection pressure is hard, the frequency of the genes in the population shifts. If we start selecting for a certain trait in organisms we end up losing variation (even passed variation) through generations.

Related Questions

In 1908 Hardy and Weinberg published papers showing that the binomial or multinomial could be applied in genetics to predict the frequencies of genotypes when allele frequencies where known. The formal algebraic proof of this Hardy-Weinberg Equilibrium Law assumes that there is no mutation in the population. This assumption is necessary, because a. organisms reproduce sexually and litter or family sizes vary. b. populations will exhibit random sampling changes in allele frequency. c. populations are not infinite and the Hardy-Weinberg proof is only a very crude approximation when natural selection is acting. d. populations are not closed and reproduce both sexually and asexually so an infinite size population is required to preserve genetic variation. e. allowing alleles to change would alter their frequencies.

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1 Explain at least 3 ways that selection can preserve genetic variation.

2 Explain how selection affects differently: dominant vs recessive traits; homozygotes vs heterozygotes; and when frequency-dependence is a factor.

3 What is the source of genetic variation? How does meiosis contribute to maintenance of genetic diversity?

4Describe the preconditions for natural selection to operate and what the results of natural selection will be.

5 Use the HW equations to solve simple population genetics problems with and without selection.

6 Hardy-Weinberg equilibrium tells us the conditions under which populations will not evolve. So what types of things may lead to a population evolving? How do these things lead to populations evolving (gene frequencies changing)?

7 When is genetic drift the strongest?

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.