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Mechanisms of Evolution > Variation at the Population Level > Flashcards

Variation at the Population Level Flashcards

1
Q

What is the central issue in population genetics?

A

Genetic variation

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2
Q

What are the 3 questions about genetic variation in population genetics?

A
  1. What is the extent within populations
  2. Why is it there
  3. How does it change over many generations
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3
Q

What is the gene pool?

A

All alleles of every gene in a population

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4
Q

What do population geneticists study?

A

Genetic variation within the gene pool and how it changes from one generation to the next

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5
Q

What is a phenotype?

A

Characteristic of an individual organism

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6
Q

What is a genotype?

A

Genetic constitution of an individual

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7
Q

What is a locus?

A

Place on a chromosome, gene that occupies a site

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8
Q

What is an allele?

A

A particular form of a gene, distinguishable by its effects on phenotype

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9
Q

What is a haplotype?

A

A set of alleles that is a DNA segment that can be distinguished from homologous sequences

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10
Q

What is a gene copy?

A

Number of representatives of a gene. Ex. 200 gene copies with 100 2N individuals

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11
Q

What is an allele frequency?

A

Relative proportion of a particular allele at a particular locus in a population, the relative commonness or rarity of an allele

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12
Q

What is a genotype frequency?

A

Relative proportion of a particular genotype in a population

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13
Q

What is a population?

A

A group of individuals of the same species living in the same region at the same time

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14
Q

What is a deme?

A

A smaller local population that is part of a larger population

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15
Q

Why do demes have different gene pools than other demes within a larger population?

A

They are often isolated by moderate geographic barriers and are more likely to interbreed with each other

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16
Q

How do you calculate the total number of alleles in a diploid population?

A

Number of individuals x 2

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17
Q

How do you calculate the total number of a certain allele in a population?

A

Add two copies for each homozygote and one copy for each heterozygote

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18
Q

How do you calculate the allele frequency in a population?

A

Number of copies of an allele in a population/ total number of gene copies in a population

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19
Q

How do you calculate the genotype frequency in a population?

A

Number of individuals with a particular genotype in a population/ total number of individuals in a population

20
Q

What should the total frequency of all alleles add up to?

A

1

21
Q

What is a monomorphic gene? What should the allele frequencies be?

A

A gene with only 1 allele. The frequency will be 1 or close to 1

22
Q

What is the Hardy-Weinberg equilibrium?

A

A simple mathematical expression that relates allele frequencies and genotype frequencies in a population

23
Q

Is the Hardy-Weinberg equilibrium a null or alternative hypothesis?

A

Null hypothesis. Predicts that allele and genotype frequencies will not change over the course of many generations

24
Q

What are the 5 assumptions of the Hardy-Weinberg equilibrium?

A
  1. No mutations
  2. No gene flow
  3. Random mating
  4. No natural selection
  5. Extremely large population
25
Q

What does it mean if the assumptions of the Hardy-Weinberg equilibrium are met?

A

The population is not evolving

26
Q

Why does the Hardy-Weinberg equilibrium assume no mutations?

A

Mutations will modify the gene pool

27
Q

Why does the Hardy-Weinberg equilibrium assume random mating?

A

Individuals showing preference in breeding will change genotype frequencies

28
Q

Why does the Hardy-Weinberg equilibrium assume large populations?

A

Small populations are very prone to random genetic drift

29
Q

Why does the Hardy-Weinberg equilibrium assume no gene flow?

A

Immigration and emigration will change allele frequencies

30
Q

Why does the Hardy-Weinberg equilibrium assume no natural selection?

A

Natural selection will lead to certain alleles becoming more common and other alleles becoming less common

31
Q

What does it mean when any of the Hardy-Weinberg equilibrium assumptions are violated?

A

The population is evolving

32
Q

What is the Hardy-Weinberg equilibrium formula for a gene with 2 alleles?

A

p^2 + 2pq + q^2 = 1

33
Q

What is p^2 in the Hardy-Weinberg equilibrium formula?

A

The genotype frequency of homozygous dominant individuals in the population

34
Q

What is 2pq in the Hardy-Weinberg equilibrium formula?

A

The genotype frequency of heterozygous individuals in the population

35
Q

What is q^2 in the Hardy-Weinberg equilibrium formula?

A

The genotype frequency of homozygous recessive individuals

36
Q

Does the Hardy-Weinberg equilibrium describe a hypothetical or real population?

A

Hypothetical. In reality none of the assumptions would likely be met

37
Q

What is p in the Hardy-Weinberg equilibrium?

A

Allele frequency of dominant allele

38
Q

What is q in the Hardy-Weinberg equilibrium?

A

Allele frequency of the recessive allele

39
Q

How might a natural population be in Hardy-Weinberg equilibrium?

A

A population can be evolving at some genes and be in Hardy-Weinberg equilibrium at other genes

40
Q

How is the phenylketonuria locus in Hardy-Weinberg equilibrium?

A

It is an autosomal recessive disorder. There is low mutation rate, mate selection is random with respect to that gene, natural selection can only act on homozygous recessive individuals that don’t follow the diet, population is large, and migration has no effect

41
Q

What does it mean when a population is at Hardy-Weinberg equilibrium?

A

Allele frequencies are not changing from generation to generation

42
Q

What are the steps to determine if a population is at Hardy-Weinberg equilibrium?

A
  1. Calculate allele frequencies
  2. Calculate the expected genotype frequencies (using p^2, 2pq, and q^2)
  3. Multiply genotype frequencies by the population size to get the expected number of individuals
  4. Compare the genotype frequencies in a population with the expected number of individuals
  5. If expected number of individuals with that genotype is + or - 5% of the number of individuals with that genotype are the same, the population is at Hardy-Weinberg equilibrium
43
Q

What is sympatric population variation?

A

Variation among populations with overlapping geographic distributions

44
Q

What is parapatric population variation?

A

Variation among neighbouring populations that are adjacent, but don’t overlap

45
Q

What is allopatric population variation?

A

Populations that are separated by geographic barriers

46
Q

What is a subspecies?

A

A recognizable distinct population occupying a different geographic area from others of the same species

47
Q

What is a cline?

A

Gradual change in a character or allele frequencies over geographic distance

Mechanisms of Evolution (20 decks)

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