Lecture 10- Population genetics Flashcards

1
Q

Requirements for natural selection to occur

A
  • variation in traits
  • traits vary in how the impact survival/ reproduction
  • traits are heritable
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2
Q

genetic variation

A

refers to the differences in genes or other DNA sequences among individuals

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3
Q

phenotype

A

physical features expressed by the genotype

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4
Q

Discrete traits

A

single gene determines phenotypic differences and can usually be classified on an either-or basis

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5
Q

Quantitative traits

A

two or more genes usually vary the phenotype in gradations along a continuum

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6
Q

Neutral variation

A

differences in DNA sequence that do not confer a selective advantage or disadvantage.

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7
Q

synonymous mutations

A

change in the dna sequence that codes for amino acids but does not change the encoded AA

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8
Q

Nonsynonymous mutation

A

change the protein sequences and are frequently subjected to natural selection

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9
Q

what prevents natural selection from reducing genetic variation to only the favorable alleles?

A
  • Recessive alleles hidden from selection i heterozygotes
  • heterozygote advantage
  • selection can preserve variation
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10
Q

Sexual selection

A

individuals with certain inherited characteristics are more likely than others of the same sex to obtain mates

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11
Q

intrasexual

A

individuals of one sex compete directly for mates of the opposite sex

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12
Q

intersexual

A

individuals of one sex are choosy in selecting their mates from the other sex

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13
Q

sexual dimorphism

A

a difference in secondary sexual characteristics between males and females

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14
Q

frequency-dependent selection

A

fitness of a phenotype depends on how common it is in the population

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15
Q

negative frequency dependent selection

A

rare genotypes have a fitness advantage

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16
Q

positive frequency dependent selection

A

common genotypes have a fitness advantage

17
Q

relative fitness

A

contribution an individual makes to the gene pool of the next generation relative to the contributions of others

18
Q

relative fitness is determined by the

A

survival/ reproductive rate of a genotypic relative to the maximum survival/ reproductive rate of other genotypes

19
Q

Most fit genotype should always have a relative fitness of

20
Q

if reproductive rates are all equal (RF)

A

each survival rate divided by the highest survival rate

21
Q

If survival rates are all equal (RF)

A

each reproductive rate divided by the highest reproductive rate

22
Q

Selection coefficient (s)

A

the relative strength of selection acting against a genotype
- s= 1- w w= relative fitness

23
Q

selection coefficient of 0 means

A

genotype is not being selected against (strong)

24
Q

selection coeff of 1 means

A

total selection, individuals produce no viable offspring

25
selection coeff of 0.1 means
individuals with that genotype produce offspring at 90% of the fittest genotype
26
P (frequency of A) + q (frequency of a) =
1, this will always be true
27
Hardy-Weinberg principle
predicts what genotype frequencies and allele frequencies will occur in the next generation
28
the Hardy- Weinberg principle assumes evolution
is not occuring
29
Assumptions of Hardy- Weinberg Equilibrium
1. NO selection 2. No mutation 3. No migration 4. Large population 5. random mating
30
Gene pool
all of the alleles from all the gametes produced in each generation
31
Calculate the frequency of alleles
[2(# homozygous individuals) + # of alleles from heterozygous individuals] / total # alleles
32
After calculating p, how do you find q?
q= 1-p
33
Calculate the expected frequency of homozygous dominant
p^2
34
Calculate the expected homozygous recessive
q^2
35
Calculate the expected heterozygous frequency
2pq
36
How to tell if a population is in HW equilibrium?
If the expected frequencies are equal to the observed frequencies.
37
How to calculate the expected # of individuals for that genotype
Multiply the frequency by the total number of individuals
38
Can you always calculate allele frequencies from genotype frequencies?
Yes you can because the genotype predicts the phenotype
39
Can you always calculate genotype frequencies from allele frequencies?
sometimes, you can if the population is in HW equilibrium