Lecture 17. The Principles of Population Genetics Flashcards

1
Q

What does genetic variation diploid populations arise from ?

A

Mutation and sexual reproduction

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2
Q

What does mutation allow ?

A

New variants

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3
Q

What does sexual reproduction allow ?

A

Variations to be continuously recombined in unique formations

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4
Q

What are a pair of homologous chromosomes defined by ?

A

Their ability to pair up during meiosis

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5
Q

What is a locus ?

A

A fixed position on a chromosome

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6
Q

What are alleles ?

A

Alternate versions of the DNA sequences that occur at the same locus on homologous chromosomes

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7
Q

What are the most commonly observed types of mutation ?

A

Single nucleotide variant

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8
Q

What is the genotype ?

A

The genetic material possessed by an individual at a given locus

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9
Q

What is the gene pool ?

A

The sum of all alleles in the breeding members of a population at any given time

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10
Q

In a diploid population of N individuals how many N alleles is there at an autosomal locus ?

A

2N alleles

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11
Q

What do we describe the gene pool in terms of ?

A

Allele and genotype frequencies

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12
Q

What is the formula for allele frequency F(A) ?

A

Allele count/Total number of alleles

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13
Q

What is the formula for a biallelic variant ?

A

F(A) + F(a) = p + q = 1

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14
Q

What is a single nucleotide polymorphism ?

A

A relatively common single nucleotide variant

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15
Q

What is a minor allele ?

A

Low frequency in the population

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16
Q

What is the major allele ?

A

Higher frequency in population

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17
Q

What is the genotypic frequency formula F(AA) ?

A

Genotype count/Total number of individuals

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18
Q

What is the genotypic frequency for a biallelic variant ?

A

F(AA) + F(Aa) + F(aa) = 1

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19
Q

What is a core concept if we have observed the genotype frequencies of a population ?

A

We can calculate the allele frequencies

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20
Q

What is a core concept about knowing the allele frequencies of a population ?

A

We can predict the expected genotype frequencies

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21
Q

When is a population in hardy weinberg equilibrium ?

A

If its observed genotype and allele frequencies do not change through the generations. They remain constant

22
Q

What does it take to bring genotypes to equilibrium proportions ?

A

One generation if random mating

23
Q

What does hardy weinberg equilibrium require ?

A
  1. Random combination of alleles at each generation - random mating
  2. No change in allele frequencies between generations - no evolution
24
Q

What are some violations to random mating ?

A
  1. Geography ie setting a limit
  2. Phenotype
  3. Interbreeding
25
What is the principle of random mating ?
All other individuals in the population must be equally likely to be chosen as a mate
26
What is a characteristic of the Wahlund effect ?
Lack of heterozygotes
27
What is the wahlund effect
Non random mating
28
What does non-random mating not change ?
Allele frequencies
29
Is a population in hardy weinberg equilibrium evolving ?
No
30
If there is still random mating in the observed genotype what will their frequencies do ?
They will match those expected within any single generation
31
What are the violations in the hardy weinberg equilibrium that lead to evolution ?
1. Mutation 2. Genetic drift 3. Gene flow/migration 4. Selection
32
What does mutation do ?
Changes the allele frequency by creating a new variant
33
How will a mutation change the minor allele frequency at an invariant locus ?
Change it from 0 to 1/2N
34
What is genetic drift also known as ?
Sampling error
35
What is genetic drift ?
Alleles are sampled at random from the gene pool to contribute to the next generation
36
In genetic drift, when is error smaller ?
The larger the sample size
37
Where is random drift stronger ?
In smaller populations
38
Where is random drift weaker ?
In larger populations
39
What are some extreme examples of genetic drift ?
1. Population bottleneck | 2. Founder effect
40
What is population bottleneck ?
Reduction in overall population size due (chance)
41
What is the founder effect ?
Isolation of a small fraction of the population from the larger group
42
What is gene flow ?
The movement of genetic material from one population to another
43
What does isolation lead to ?
Divergence in allele frequencies
44
What is genetic differentiation ?
Accumulation of allele frequency differences due to restricted gene flow
45
What allows for gene flow ?
A reduction in the barriers to mating
46
What is admixture ?
Gene flow between two or more genetically distinguishable populations
47
What can be considered if gene flow is high enough ?
The two populations can be considered a single random mating population
48
What happens if gene flow is low enough ?
Subpopulations can be detected through allele frequencies differences called population structure
49
Where are clines observed ?
When gene flow occurs more frequently between neighboring groups
50
Why are populations always evolving ?
1. Mutation is inevitable 2. Population sizes are finite 3. The earth is dynamic - continuous isolation and flow
51
What is selection ?
A non-random change in allele frequencies due to interactions between phenotype and environment