BIO120H1 Lecture Notes - Lecture 5: Genetic Drift, Population Genetics, Natural Selection

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R. a fisher, j. b. s haldane, s. wright: mutation. 1. increases genetic diversity: ultimate source for genetic variation, caused by errors during replication (not directed, recombination. Introduces new combinations of mutations into a population: random genetic drift. 1. (decreases genetic diversity: random sampling effects every generation, becomes more important as populations become smaller, you can get evolution with natural selection, by chance, natural selection. 1. increases genetic diversity: migration in uences the structuring of diversity over a large spatial scale. Average frequency of heterozygous individuals per gene loci. Less t types maintained by repeated mutation: diverse selective forces favouring diversity, heterozygote advantage, frequency-dependent selection, tness varies in space and time. I. e. rare-types are always favoured: variation selectively neutral, different types do not differ in their tness hence not eliminated by selection. Low polymorphism: wild type is normal genotype. How natural selection is actively varying population genetics. There should be plenty genetic variations in that case.

Related Questions

Need help with evolution questions:

1.) A haplotype is best defined as the ________________.

	haploid genotypes of all the gametes produced by a diploid individual

ABO blood type conferred by an individual gamete

genotype of either the paternal or maternal chromosomal complement

multilocus genotype of a chromosome or gamete

2.) Which of the following statements regarding linkage disequilibrium is true?

Exists when D is less than zero, but not when it is greater than zero.

Is reduced by sexual reproduction.

Is increased by crossing-over during meiosis.

Is increased by any random sampling error that happens to create or destroy certain chromosome genotypes but not others.

Is reduced by selection that favors certain combinations of genotypes.

3.) Selection on multilocus genotypes in random-mating populations leads to linkage disequilibrium when _______________.

it reduces mutation rates

it eliminates all haplotypes from the population

it prevents crossing-over during meiosis

some allele combinations confer greater fitness than do others

4.) When two loci are in linkage equilibrium, the allele carried on a chromosome at one locus is independent of the allele carried on the chromosome at another locus. When this is the case, _________________.

allele frequencies will not change over time

the two loci (or, more specifically, their protein products) do not interact

the frequency of each haplotype can be calculated by multiplying the frequency of its two alleles

all possible haplotypes occur at equal frequency

5.) Which of the following accurately characterize(s) Muller's ratchet model for the selective advantage of sexual reproduction?

Drift establishes linkage disequilibrium because multilocus genotypes with few mutations are eliminated by chance events.

In populations without sexual reproduction, deleterious mutations accumulate, eventually imposing such a burden that the population goes extinct.

Sex is favored selectively because it recreates the zero-mutation genotypes lost due to drift.

All of the above correctly characterize Muller's ratchet model for the evolution of sexual reproduction.

6.) The genetic signature of recent positive selection on a locus is _______________.

high frequency and low linkage disequilibrium

low frequency and low linkage disequilibrium

low frequency and high linkage disequilibrium

high frequency and high linkage disequilibrium

7.) Sexual reproduction is advantageous both in changing environments and in constant environments, compared to asexual reproduction.

True

False

8.) Sexual reproduction causes genetic recombination via crossing-over, which combines genotypes from different parents.

True

False

9.) One reason sex may be maintained in natural populations is proposed by the "Red Queen Hypothesis", which states that.....

genotypes created by sex are created by natural selection over and over

recombination creating novel genotypes that can resist infection by parasites

mutation load is reduced by novel adaptive mutations

the ability of sex to fix multiple

BIO120H1 Lecture Notes - Lecture 5: Genetic Drift, Population Genetics, Natural Selection

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