Exam 8: Evolution at Multiple Loci: Linkage and Sex

Certain loci that are in linkage disequilibrium with alleles of interest can be used as markers,which can then be useful in reconstructing the history of those alleles in populations.One such marker/allele is described in your text,where the allele in question has an insertion mutation,rendering an enzyme (glucocerebrosidase,or GBA)nonfunctional.The decay curve for linkage disequilibrium between this marker (named D1S305)and the nonfunctional GBA allele is shown in the accompanying figure.The orange lines show the present level of linkage disequilibrium and the inferred number of generations elapsed since the most recent common ancestor.Assuming an average generation time of 25 years,how many years total will be required for the linkage disequilibrium reach 0.2?

According to the accompanying figure,we can conclude that ________.

The explanation for the accumulation of deleterious alleles in asexual populations over time,with the resulting genetic load,is known as ________.[two words]

Muller's ratchet posits that in a finite asexual population,the number of deleterious alleles will increase over time.The accumulation of these deleterious alleles is called ________.

When genotypes at one locus of a chromosome are independent of genotypes at another locus of the same chromosome,the two loci are ________.

Research and analysis has documented that Muller's ratchet works ________.

A principle advantage of sexual reproduction is that it ________.

Explain and describe the three ways in which linkage disequilibrium can be produced in a population.Refer to the accompanying figures to support your explanation.

The principal advantage of sexual reproduction is that it "reshuffles the genetic deck." The creation of new combinations of alleles during sexual reproduction-complete with outbreeding and meiosis with crossing over-is called ________.[two words]

The creation of new combinations of alleles,as a consequence of sexual reproduction with meiosis,is called ________.

Please refer to the accompanying figures.Is the population in linkage equilibrium or linkage disequilibrium? Explain,drawing on the evidence in the figures.

Haploid genotypes involving two loci,such as AB,Ab,aB,and ab,are known as an organism's ________.

When considering two loci on a chromosome,the loci are said to be in ________,[two words] when the genotype at one locus is independent of the other.

Which of the following choices is NOT a potential disadvantage to sexual reproduction?

Alleles that are relatively new to a population and have been subject to positive natural selection are characterized by having ________.

An advantage to studying linkage disequilibrium is that ________.

Which of the following conditions accurately represent Muller's ratchet,in terms of the selective advantage of sexual reproduction?

In cases where a perpetual "arms race" occurs between biological antagonists,such as parasites and their hosts,sex is favored because it reduces linkage disequilibrium by recreating missing genotypes in an oscillating fashion.This hypothesis is called the ________ [two words] hypothesis.

Drawing on the accompanying graphs for support,describe and explain the way in which Muller's ratchet works in asexual populations.

If there is a nonrandom association between the genotypes at two loci on a chromosome,the loci are said to be in ________.[two words]