Lecture 17. The Principles of Population Genetics

Question 1

What does genetic variation diploid populations arise from ?

Answer 1

Mutation and sexual reproduction

Question 2

What does mutation allow ?

Answer 2

New variants

Question 3

What does sexual reproduction allow ?

Answer 3

Variations to be continuously recombined in unique formations

Question 4

What are a pair of homologous chromosomes defined by ?

Answer 4

Their ability to pair up during meiosis

Question 5

What is a locus ?

Answer 5

A fixed position on a chromosome

Question 6

What are alleles ?

Answer 6

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

Question 7

What are the most commonly observed types of mutation ?

Answer 7

Single nucleotide variant

Question 8

What is the genotype ?

Answer 8

The genetic material possessed by an individual at a given locus

Question 9

What is the gene pool ?

Answer 9

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

Question 10

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

Answer 10

2N alleles

Question 11

What do we describe the gene pool in terms of ?

Answer 11

Allele and genotype frequencies

Question 12

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

Answer 12

Allele count/Total number of alleles

Question 13

What is the formula for a biallelic variant ?

Answer 13

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

Question 14

What is a single nucleotide polymorphism ?

Answer 14

A relatively common single nucleotide variant

Question 15

What is a minor allele ?

Answer 15

Low frequency in the population

Question 16

What is the major allele ?

Answer 16

Higher frequency in population

Question 17

What is the genotypic frequency formula F(AA) ?

Answer 17

Genotype count/Total number of individuals

Question 18

What is the genotypic frequency for a biallelic variant ?

Answer 18

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

Question 19

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

Answer 19

We can calculate the allele frequencies

Question 20

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

Answer 20

We can predict the expected genotype frequencies

Question 21

When is a population in hardy weinberg equilibrium ?

Answer 21

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

Question 22

What does it take to bring genotypes to equilibrium proportions ?

Answer 22

One generation if random mating

Question 23

What does hardy weinberg equilibrium require ?

Answer 23

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

Question 24

What are some violations to random mating ?

Answer 24

1. Geography ie setting a limit
2. Phenotype
3. Interbreeding

Question 25

What is the principle of random mating ?

Answer 25

All other individuals in the population must be equally likely to be chosen as a mate

Question 26

What is a characteristic of the Wahlund effect ?

Answer 26

Lack of heterozygotes

Question 27

What is the wahlund effect

Answer 27

Non random mating

Question 28

What does non-random mating not change ?

Answer 28

Allele frequencies

Question 29

Is a population in hardy weinberg equilibrium evolving ?

Answer 29

No

Question 30

If there is still random mating in the observed genotype what will their frequencies do ?

Answer 30

They will match those expected within any single generation

Question 31

What are the violations in the hardy weinberg equilibrium that lead to evolution ?

Answer 31

1. Mutation
2. Genetic drift
3. Gene flow/migration
4. Selection

Question 32

What does mutation do ?

Answer 32

Changes the allele frequency by creating a new variant

Question 33

How will a mutation change the minor allele frequency at an invariant locus ?

Answer 33

Change it from 0 to 1/2N

Question 34

What is genetic drift also known as ?

Answer 34

Sampling error

Question 35

What is genetic drift ?

Answer 35

Alleles are sampled at random from the gene pool to contribute to the next generation

Question 36

In genetic drift, when is error smaller ?

Answer 36

The larger the sample size

Question 37

Where is random drift stronger ?

Answer 37

In smaller populations

Question 38

Where is random drift weaker ?

Answer 38

In larger populations

Question 39

What are some extreme examples of genetic drift ?

Answer 39

1. Population bottleneck

2. Founder effect

Question 40

What is population bottleneck ?

Answer 40

Reduction in overall population size due (chance)

Question 41

What is the founder effect ?

Answer 41

Isolation of a small fraction of the population from the larger group

Question 42

What is gene flow ?

Answer 42

The movement of genetic material from one population to another

Question 43

What does isolation lead to ?

Answer 43

Divergence in allele frequencies

Question 44

What is genetic differentiation ?

Answer 44

Accumulation of allele frequency differences due to restricted gene flow

Question 45

What allows for gene flow ?

Answer 45

A reduction in the barriers to mating

Question 46

What is admixture ?

Answer 46

Gene flow between two or more genetically distinguishable populations

Question 47

What can be considered if gene flow is high enough ?

Answer 47

The two populations can be considered a single random mating population

Question 48

What happens if gene flow is low enough ?

Answer 48

Subpopulations can be detected through allele frequencies differences called population structure

Question 49

Where are clines observed ?

Answer 49

When gene flow occurs more frequently between neighboring groups

Question 50

Why are populations always evolving ?

Answer 50

1. Mutation is inevitable
2. Population sizes are finite
3. The earth is dynamic - continuous isolation and flow

Question 51

What is selection ?

Answer 51

A non-random change in allele frequencies due to interactions between phenotype and environment