BIOL 3463 Lecture 3: BIO3463, lecture 3

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1 Sep 2018

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What creates linkage disequilibrium: selection and genetic drift can shift a population from equilibrium to disequilibrium, if a particular allele is advantageous, selection could drive the population further from equilibrium. Random genetic drift could cause a to convert to a on an ab chromosome. This creates a single ab chromosome and puts the population into linkage disequilibrium because we are missing the possible haplotype ab: but, this would only happen in a finite population. In an infinite population, the mutation converting a to a would happen many times and at no point would ab be missing. What eliminates linkage disequilibrium: genetic recombination tends to randomize genotypes at one locus with respect to genotypes at another. Evolution of sex sexual vs. asexual assumptions. Assumption 2 was tested by developing an (cid:498)asexual strain(cid:499) and a (cid:498)sexual strain(cid:499) of flour beetles. Despite the asexual black beetles producing more offspring each generation, eventually the evolving sexual strain completely eliminated the non-evolving asexual strain.

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

BIOL 3463 Lecture 3: BIO3463, lecture 3

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