ch 25

Question 1

genetic rescue

Answer 1

– introduction of new genetic variation into an inbred population

Question 2

Small populations lose….

Answer 2

genetic variation over time through inbreeding and genetic drift (change in allelic frequency).

Question 3

Migration introduces…

Answer 3

new genetic variation that counteracts the effects of genetic drift and inbreeding.

Question 4

Almost all organisms exhibit

Answer 4

phenotypic
variation.

Much of this variation is hereditary

Question 5

Genetic variation is the basis of

Answer 5

all evolution.

The extent of genetic variation within a population affects its potential to adapt to environmental change

Question 6

Mendelian population

Answer 6

– a group of interbreeding, sexually reproducing individuals that have a common set of genes – the gene pool.

Question 7

Genotypic frequency:

Answer 7

Number of individuals possessing the genotype divided by total number of individuals in sample

Question 8

Genotypic frequency equations

Answer 8

f(AA) = # AA individuals/N

f(Aa) = # Aa individuals/N

f(aa) = # aa individuals/N

N: total # of individuals

f: frequency each genotype.

The sum of all genotypic frequencies always equals 1.

Question 9

Allelic frequency

Answer 9

Number of copies of a particular allele present in a sample divided by total number of alleles

The gene pool of a population can also be described in terms
of allelic frequencies.

Question 10

Allelic frequency equation

Answer 10

frequency of an allele =
# copies of the alleles /
# copies of all alleles at
the locus in a population

Question 10

Calculating allelic frequencies

Answer 10

look at slide 7

For a locus with only two alleles (A and a), the frequencies are
usually represented by p (dominant) and q(recessive).

Question 11

X-linked loci allelic freq

Answer 11

slide 8

When calculating allelic frequencies for genes at the X-linked loci, we apply the same principles, but females possess 2 X chromosomes (and therefore has two X-linked alleles)

Question 12

How many alleles are in this population? 6129 individuals

Answer 12

12,258

Question 13

What is the allele frequency of LM and LN?
LM indiv= 1787
LMN indiv= 3039
LN indiv= 1303

Answer 13

LM = (1787*2) + 3039/12,258 =0.54

LN = (1303*2) + 3039/12,258 =0.46

should equal 1

Question 14

The Hardy-Weinberg principle

Answer 14

mathematical relationship
between allele frequencies and genotype frequencies

allows prediction of population’s genotype frequencies from its allele frequencies

Question 15

The Hardy-Weinberg principle equations

Answer 15

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

Question 16

When are we in HWE and accept hypoth

Answer 16

If allele frequencies are the same

if changed not in HWE and reject null

Question 17

random mating

Answer 17

The key assumption underlying the Hardy-Weinberg principle

If mating is random and no differential survival or
reproduction exists among members of the
population, the Hardy-Weinberg genotype
frequencies persist generation after generation

Question 18

Assumptions for Hardy-Weinberg

Answer 18

Populations are usually not in Hardy Weinberg equilibrium (at least, not for all of
the genes in their genome).

Populations tend to evolve: the allele
frequencies of at least some of their genes
change from one generation to the next

Question 19

Exceptions to the Hardy Weinberg Principle

Answer 19

Nonrandom mating
Unequal survival
Population subdivision
Migration
Finite population size

Question 20

genetic drift

Answer 20

Small population size can cause a random
change in allele frequencies

due to a
sampling effect.
– Sampling effects are most important when the
allele is present in a small number of copies.

Question 21

random genetic drift

Answer 21

Uncertainties of genetic transmission can lead to random changes in allele frequencies

The alleles of segregating genes are randomly incorporated into gametes. There is always uncertainty as to which allele a given offspring will receive

Question 22

large VS small pop sizes in genetic drift

Answer 22

In large populations, the effect of genetic drift is
minimal.

In small populations, genetic drift may be the
primary evolutionary force.

Question 23

natural selection

Answer 23

selection for survival and
reproduction in the face of competition

The mechanism that changes
the physical and behavioral characteristics of a species

Question 24

Fitness

Answer 24

symbolized by W, is the relative reproductive success of a genotype
– the reproductive success of one genotype compared to
another genotype in the population!

Question 25

Relative Fitness

Answer 25

Does not give the absolute reproductive abilities of the
different genotypes in the two habitats.

Does tell us how well each genotype competes with the other genotypes within a particular environment.

If s1 = 1, then aa is effectively a lethal genotype (it’s relative fitness is 0), and we would expect natural selection to reduce the frequency of the a allele in the population.

If s1 is very small, 0.01, natural selection will still reduce the frequency of allele a, but very slowly.

Question 26

To calculate fitness for each genotype

Answer 26

, the mean number of
offspring produced by each genotype is divided by the mean number of offspring produced by the most prolific genotype.

slide 49

To calculate fitness of each genotype;
W 1,1 = 10/10 = 1
W 1, 2 = 5/10 = 0.5 - use 10 bc most fit NOT total
W 2, 2 = 2/10 = 0.2

Question 27

calculating selection coefficient

Answer 27

-In each environment, the fitness of the superior genotype(s) is defined as 1

-The fitness of the inferior genotype(s) is expressed as a deviation from 1

-The fitness deviation (s) is the selection coefficient,
which is the relative intensity of selection against a genotype.

To calculate selection coefficient (1-W);
s11 = 0
s12 = 0.5
s22 = 0.8