Lecture 9

Question 1

Population genetics

Answer 1

the study of the genetics of populations
- studies both the systematic and random forces of evolution and attempts to elucidate the fundamental mechanisms that cause genetic changes in a population over time

Question 2

Population genetics focus their attention on

Answer 2

a Mendelian population

Question 3

Mendelian population

Answer 3

a group of interbreeding, sexually reproducing individuals that have a common set of genes

Question 4

gene pool

Answer 4

a common set of genes

Question 5

Population geneticists are interested in

Answer 5

the frequencies of the alleles in the population and how they change (or do not change) over time

Question 6

Major gap of Darwin’s theory of evolution

Answer 6

it offered no explanation for the origin of variation and could not explain how particular variants are inherited

Question 7

Mendel’s principle

Answer 7

Traits are determined by genes, which segregate different alleles, and genes are transmitted to the offspring in gametes produced by their parents

Question 8

Genotypic frequency

Answer 8

• the proportion of a particular genotype within a population
• calculated by taking (# individuals w/ genotype)/(total)
• also the relative frequency
• should add to 1

Question 9

Allelic frequency

Answer 9

-the proportion of a particular allele within a population

Question 10

Gametic Array

Answer 10

• percent of each gamete present

- calculated by taking 1/2 hetero + all homo

Question 11

Hardy-Weinburg Equilibrium

Answer 11

allows us to predict a population’s genotypic frequencies from its allelic frequencies

• p frequency of A
• q frequency of a

p^2 + 2pq + q^2
AA + Aa + aa

Question 12

Assumptions of Hardy Weinberg

Answer 12

• no migration
• no mutation
• no selection (all genotypes are equally fit)
• random mating (random pairing of gametes)
• infinitely large population
  apply to a single locus

Question 13

Heterozygocity

Answer 13

fraction of the population that is heterozygous

Question 14

Homozygocity

Answer 14

fraction of the population that is homozygous

Question 15

Monomorphic

Answer 15

when the frequency of the most frequent alley is >/= .99

Question 16

Polymorphic

Answer 16

when frequency of most frequent alley is </= .99

Question 17

The frequencies of the heterozygotes is greatest when

Answer 17

the allelic frequencies are equal

p=q=0.5

Question 18

When the frequency of one allele is high

Answer 18

most of the individuals are homozygotes

Question 19

Implications of HW

Answer 19

• a population cannot evolve if it meets the HW assumptions

- when a population is in HW equilibrium, the genotypic frequencies are determined by the allelic frequencies

Question 20

Chi Square Test for Hardy-Weinberg Equilibrium

Answer 20

1. Calculate allelic frequency
   - f(A)=AA+1/2Aa/total=p
   - f(a)=aa+1/2Aa/total=q
2. Calculate expected genotypic frequency
   f(AA)=p^2
   f(Aa)=2pq
   f(aa)=q^2

Question 21

Genetic hypothesis

Answer 21

The population of (organism) has Hardy-Weinberg proportions for the _______ locus

Question 22

degrees of freedom

Answer 22

genotypes - # alleles

Question 23

Genetic conclusion

Answer 23

The ____ locus in _____ is (consistent with or not consistent with) Hardy-Weinberg proportions at the 5% significance levels

Question 24

Mutation calculation

Answer 24

A mutates to a - u
a mutation to A - v

p’=(1-u)p+v(1-p)

p=frequency of A allele
1-p=frequency of a allele

keep all decimal digits on mutation problems

Question 25

Migration calculation

Answer 25

P=frequency of A in the mainland p=frequency of A allele on island initially m=proportion of migrants after immigration occurred=probability that a parent will come from the mainland 1-m=probability that a parent will come from the island=proportion of total population after migration that was from the island p'=frequency of A allele (on the island) after migration p'=(1-m)p+mP

Question 26

fitness

Answer 26

the relative reproduction success of a genotype compared with the reproductive fitness of another genotype.

Question 27

components of fitness

Answer 27

- viability to reproduction - fertility (birthrate) - fecundity (gamete production)

Question 28

Assortative mating

Answer 28

- Mating is based on phenotypes - can be positive or negative - Ex. humans exhibit positive assortative mating for height - usually for a particular trait and will affect only those genes that encode the trait (and genes closely linked to them)

Question 29

Inbreeding

Answer 29

- mating of related individuals - this is a form of positive assortative mating for relatedness but it differs from other forms because it affects all genes, not just those that determine the trait for which the mating preference exists - leads to an increase in the number of homozygotes and a decrease in the number of heterozygotes

Question 30

When a population size is small

Answer 30

the gametes that unite to form individuals of the next generation carry a sample of alleles present in the parental gene pool

Question 31

sampling error

Answer 31

deviation from an expected ratio due to limited sample size

Question 32

genetic drift

Answer 32

- a change in allelic frequency due to sampling error | - leads to random fixation and loss of alleles over time

Question 33

Causes of genetic drift

Answer 33

- population reduction for several generations - founder effect - genetic bottleneck

Question 34

population reduction for several generations

Answer 34

may be due to limitations in space, food, or some other critical resource

Question 35

founder effect

Answer 35

establishment of a population by a small number individuals

Question 36

genetic bottleneck

Answer 36

a population undergoes a drastic reduction in population size

Question 37

fixation

Answer 37

an allele may eventually reach a frequency of 1

Question 38

genotypic array

Answer 38

individuals of each genotype/ total number of individuals

Question 39

Nonrandom mating

Answer 39

affects the way in which alleles combine to form genotypes and alters the genotypic frequencies of a population