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Flashcards in Quantitative Genetics Deck (20):

linkage disequilibrium

the occurrence of combinations of allies or genetic markers in a population more ore less often then would be expected from random haplotype formation from alleles based on their frequencies


Random discrepancy between theoretical expectations and actual results is

sampling error


Mutations come in four kinds:

1. lethal
2. deleterious
3. neutral
4. beneficial


transfer of alleles from
the gene pool of one population to the gene pool of
another population, aka “gene flow”.



In the Hardy-Weinberg model, genetic drift results from

violation of the
assumption of infinite population size.


Genetic drift lead to

changes in allele


Genetic drift has a more rapid and dramatic effect on allele frequencies in _____
populations than in ______ populations.

small, large


The wandering of allele frequencies produces two important and related

1. Eventually alleles drift to fixation or loss, and
2. The frequency of heterozygotes declines.


the number of breeding individuals in a
population that would show the same amount of dispersion of allele
frequencies or inbreeding as the population under consideration under
random genetic drift.

Effective population size -


______is the creation of a new allele; is the fixation of the new
allele, with or without additional mutational change.

mutation , substitution


Neutral theory -

Holds that advantageous mutations are exceedingly rare and
that most alleles of most genes are selectively neutral.


Selectionist theory -

Holds that advantageous mutations are common enough
that they cannot be ignored.


When mutation, genetic drift, and selection interact, three
processes occur:

1. Deleterious alleles appear and are eliminated by selection.
2. Neutral mutations appear and are fixed or lost by chance; and
3. Advantageous alleles appear and are swept to fixation by selection.


Functionless stretches of DNA that result from gene duplication

Pseudogenes -


suggests that some
synonymous mutations are not selectively neutral.

Codon bias (strongest in highly expressed genes)


Hitchhiking/Selective Sweep -

Can occur when strong positive selection acts on
a particular amino acid change.
• As a favorable mutation increases in frequency, neutral or even slightly
deleterious mutations closely linked to the favored site will increase in
frequency along with the beneficial locus.


refers to the effect deleterious recessive alleles (in
homozygotes) have on the average fitness of offspring in the population.

Inbreeding depression


Human activity did two things to the panther.

1. It directly reduced the size of the cat’s population.
2. It isolated the cat from other puma populations that it is closely related to—and
that it once interbred with.


If the problem for the Florida panther is reduced genetic diversity, then the solution
is gene flow. how to fix?

Migrants from other populations should bring with them the alleles that have been
lost in Florida.
Reintroduction of these lost alleles should reverse the effects of drift and eliminate
inbreeding depression.


Two mechanisms of gene duplication are thought to be among the most common
sources of new genes. !

1. Unequal crossing over!
2. Retroposition or retroduplication!