Evolution lecture 8 Flashcards
(28 cards)
haplotype
the multi-locus genotype of a chromosome or gamete
Linkage equilibrium:
two loci are in linkage equilibrium when the genotype of a chromosome at one locus is independent of its genotype another locus.
Linkage disequilibrium:
two loci are in linkage disequilibrium when there is a non-random association between a chromosome’s genotype at one locus and its genotype at another locus.
populations can have identical ________ frequencies but different _______ frequencies in LD.
allele; chromosome
Coefficient of LD
D = gABgab – gAbgaB, 0 for LE and ranges from -0.25 to +0.25
A population in ________ ________ will not change chromosome frequencies from one generation to the next.
LE
What are the three conditions for LE?
- The frequency of B on chromosomes carrying the A allele is equal to the frequency of B on chromosomes carrying the “a” allele.
- The frequency of any chromosome haplotype can be calculated by multiplying the frequencies of the constituent alleles.
- The quantity D, the coefficient of linkage disequilibrium, is equal to zero.
What creates LD in a population?
1 - selection
2 - genetic drift
3 - population admixture
population admixture
o where two populations that do not have gene flow between them come together. Wind up with unreal representation
when loci are in LD, selection at one locus can change allele frequencies at the ______.
other
How do you get rid of linkage??
Recombination
What is the recombination rate?
R, related to D. R = 0.5 when on separate chromosomes
If genes are _____ each other on the same chromosome, it takes _____ to remove LD
1 - near
2 - longer
red queen hypothesis
arms race, keep running as hard as you can to just stay in place. Need to evolve better defenses to evade pathogen attack and, pathogen needs to develop ways to get around the defenses.
The persistence of sex is a ______, because a simple model shows that ______ females should rapidly take over any population.
1 - paradox
2 - asexual
• Null model for a population in which females reproduce sexually and asexually, one each to start has two assumptions. What are they?
- A female’s reproductive mode does not affect how many offspring she makes
- A female’s reproductive move does not affect the probability that her offspring will survive
How can assumption 1 be violated?
Assumption 1 is violated in populations where the male provides resources and parental care
How can assumption 2 be violated?
Assumption 2 is violated in populations in which the male provides better genes
Outcrossing rate:
the fraction of offspring fathered by males.
Genetic load:
burden imposed by accumulating mutations in asexual species.
Muller’s ratchet:
the loss of a group by drift is much easier than its re-creation by back mutations.
____ breaks Muller’s ratchet.
sex
Sex may be advantageous because it re-creates favourable _________ genotypes that have been lost to drift.
multi-locus
When does muller’s ratchet move fastest?
small populations with mildly deleterious alleles
