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Evolution > Quest 4 > Flashcards

Quest 4 Flashcards

1
Q

Law of large numbers

A

as the size of a random sample increases, realized frequencies will be close to expected frequencies

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2
Q

genetic drift

A

random fluctuation in allele frequencies due to sampling effects in small populations

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3
Q

Wright-Fisher Model

A

Like HWE but relaxes the infinite population size assumption

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4
Q

Wright-Fisher Model assumptions

A
  1. NS is not acting on traits in question
  2. Mating is random
  3. No mutation
  4. No migration
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5
Q

selectively neutral

A

alleles with no fitness difference between them, NS does not act on the frequencies of these alleles

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6
Q

observed heterozygosity

A

fraction of individuals in the population that are heterozygous at the given locus

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7
Q

expected heterozygosity

A

fraction of heterozygotes expected under HWE model given the allele frequencies in a population

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8
Q

Ne

A

effective population size

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9
Q

Effective population size

A

The number of individuals in a population that are actively breeding

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10
Q

population bottle neck

A

brief period of small population size

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11
Q

founder effect

A

change in allele frequencies from sampling effects when a small number if individuals from a large population colonize a new area

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12
Q

leading edge expansion

A

form of drift: founder effects cause reduced genetic diversity in a newly colonized area

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13
Q

He

A

heterozygosity

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14
Q

neutral theory of molecular evolution

A

biologists look at DNA, RNA and amino acid sequences and how they change over time as opposed to phenotype

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15
Q

assumptions of neutral theory of mol evolution

A
  1. most variation in a pop. is selectively neutral.
  2. most change in DNA and amino acid sequence are selectively neutral
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16
Q

substitution

A

-new allele arises from mutation and is subsequently fixed in the population
-MOST SUBTITUTIONS ARE NEUTRAL NOT MOST MUTATIONS

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17
Q

mutation

A

a change in the genes DNA sequence to produce something different

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18
Q

Pseudogenes

A

nonfunctional, untranslated segment of DNA that arise from previously functional segment and show evolutionary history as they are derived from known homologous genes

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19
Q

positive selection

A

promotes the spread of beneficial alleles, beneficial allele will be favored in the population

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20
Q

purifying selection

A

minimizes the spread of deleterious alleles, deleterious alleles will be selected against in a poulation

21
Q

Molecular clock

A

DNA and protein sequences that evolve constantly over time among different organisms

22
Q

equidistant principle

A

if molecular changes are constant, members of a clade should be equidistant from the outgroup

23
Q

Coalescent time

A

number of generations to go back for a population to be reduced to two parental lineages. RECENCY OF COMMON ANCESTRY

24
Q

polygenic trait

A

trait that is affected by many genes simultaneously

25
Q

additive genetic effects

A

alleles of single genes combine to equal the sum of their individual effects

25
Q

Latent variation

A

-So much variation within populations that not all possible genotypes could be represented
-selection shifts allele frequencies even in the absence of mutations

26
Q

epistasis

A

effect of a gene mutation is dependent on presence or absence of mutations in one or more other genes

27
Q

haplotype

A

Set of gene copies that tend to be inherited together

28
Q

Physical Linkage

A

two genes are located on the same chromosome

29
Q

linkage disequilibrium

A

-non-random association of alleles at different loci
-loci in LD when frequency of association is higher or lower than what would be expected.

30
Q

genetic hitchhiking

A

when an allele changes frequency because it is near another gene that is undergoing a selective sweep and that is on the same DNA chain

31
Q

background selection

A

loss of surrounding alleles when a deleterious mutation is selected against

32
Q

selective sweep

A

advantageous mutation reduces variation in linked sites as it increases in frequency in the population

33
Q

3 consequences of genetic drift

A
  1. allele frequencies fluctuate over time even in the absence of NS
  2. some alleles are fixed and some lost, the fraction of heterozygotes in pop decrease over time
  3. separate populations diverge allele frequencies
34
Q

New Zealand Snappers

A

small effective population size. Have a population size of around 3 million fish but only around 200 of them can reproduce, so their Ne is 200

35
Q

divergence between populations of Lava Lizards

A

population subdivision: limited or no gene flow between subpopulations of a larger population

36
Q

Manx cats

A

founder effect: prevalence of the M allele on the Isle

37
Q

Northern Elephant Seal

A

population bottleneck: causing low levels of heterozygosity, skewed reproductive success

38
Q

Spruce trees in leading edge expansion

A

two hallmarks for genetic drift: low diversity within, high diversity between

39
Q

selection and drift interactions

A

selection and drift are not mutually exclusive, selection must be strong to reach fixation due to drift on the population.

40
Q

Neutralist and Selectionist debate

A

dispute on weather drift or selection is the primary driver of evolutionary change.

41
Q

Do molecular clocks work?

A

useful when comparing a single locus over a short time for closely related organisms

42
Q

effects of population size on coalescence

A

coalescence occurs more quickly in smaller populations compared to larger populations

43
Q

effects of selection on coalescence

A

selection drives the alleles to fixation quickly. When under positive selection coalescence occurs more quickly.

44
Q

antibiotic resistance and compensatory mutations

A

mutation at one lotus confers antibiotic resistance and a compensatory mutation at a second locus reduces the fitness cost of resistance

45
Q

Most variation seems continuous because…

A

polygenetic traits are continuous

46
Q

Ways LD can happen

A

-selection
- rate of genetic recombination
- genetic drift
- system of mating
- population structure
- genetic linkage

47
Q

How does loss of linkage disequilibrium happen?

A

meiosis with crossing over and outbreeding (asexual reproduction)

Evolution (9 decks)

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