Exam 3: Population and Evolutionary Genetics I

Question 1

define population genetics

Answer 1

study of the distribution and change in frequency of alleles within populations

Question 2

evolution is a change in _

Answer 2

gene frequency over time in a population which leads to speciation and divergence

Question 3

what can change gene frequency

Answer 3

environmental stress/pressures can modify gene expression patterns and genetic make-up

Question 4

reproductive success is measured by

Answer 4

of offspring left behind and quality/probable fitness

Question 5

there is a lot of variation in living organisms. why is that important for species survival

Answer 5

if a organism can adapt, then those minor differences/variation mean the organism has the ability to respond to changing environments to survive and reproduce

Question 6

what is it about the bighorn sheep in 1922

Answer 6

population was disappearing as there was not enough variation because hunter were killing off males (genetic drift/founder effect). Repaired variety in population by introducing a new bighorn sheep from other populations

Question 7

define population

Answer 7

group of interbreeding, sexually reproducing individuals sharing a common set of genes

Question 8

define genetic variation

Answer 8

gene frequencies are affected by evolutionary forces: mutation, gene flow, genetic drift, and nonrandom mating, natural selection

Question 9

example of gene flow

Answer 9

human beings bringing in new sheep = new individuals and new genetic material

Question 10

example of genetic drift

Answer 10

genes disappearing from population/cause of change in gene frequency by random events. usu in small populations

Question 11

nonrandom mating

Answer 11

selective selection (behavioral)

Question 12

natural selection

Answer 12

environmental influences that allow certain individuals to prosper and leave behind those advantageous genes

Question 13

what is the history of the hardy-weinberg law

Answer 13

theory to help understand process of natural selection and evolution

Question 14

calculating genotypic frequencies mean:

Answer 14

(# of individuals possessing the genotype)/(total # of individuals in sample)

Question 15

calculating allelic frequencies means:

Answer 15

(# of copies of a particular allele present in a sample)/(total # of alleles)

Question 16

loci with multiple alleles and x-linked loci are calculated

Answer 16

similarly

Question 17

definition of hardy-weinberg law

Answer 17

allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences

Question 18

hardy-weinberg law: assumptions

Answer 18

population is large, randomly mating, not affected by mutation, migration, or natural selection (rare no change in gene frequency)

Question 19

hardy-weinberg law: prediction 1

Answer 19

the allelic frequencies of a population do not change

Question 20

hardy-weinberg law: prediction 2

Answer 20

the allelic frequencies stabilize

Question 21

p^2

Answer 21

homozygous dominant allele pair frequency (1/4 cross btwn 2 hets)

Question 22

q^2

Answer 22

homozygous recessive allele pair frequency (1/4 cross btwn 2 hets)

Question 23

2pq

Answer 23

heterozygous allele frequency (1/2 cross btwn 2 hets or 2 out of 4)

Question 24

p + q = 1 when

Answer 24

there are only 2 alleles in a population

Question 25

genotype frequencies may be predicted for the next generation if hardy-weinberg assumptions hold true. Does this ever happen?

Answer 25

no; very rare. selective pressures are acting all the time on organisms causing them to evolve to adapt and survive

Question 26

frequencies of alleles can be calculated from #s of

Answer 26

genotypes

Question 27

the sum of all the genotypic of allelic frequencies in a sample always =

Answer 27

1

Question 28

when a population is in hardy-weinberg equilibrium, the proportions of genotypes are determined by

Answer 28

the frequencies of the alleles

Question 29

when the frequency of one allele is high, most of the individuals are

Answer 29

homozygotes

Question 30

the frequency of the heterozygote is greatest when

Answer 30

allelic frequencies are equal (p=q=0.5)

Question 31

positive assortative mating

Answer 31

a tendency of like individuals to mate

Question 32

negative assortative mating

Answer 32

a tendency of unlike individuals to mate

Question 33

what other sorts of nonrandom mating occur

Answer 33

nonrandom mating/inbreeding two types:

1. assortative mating (mating between individuals with similar phenotypes or among individuals that occur in a particular location) or
2. inbreeding (mating between related individuals)

Question 34

nonrandom mating may have similar consequences since

Answer 34

Both types of nonrandom mating may have similar consequences since individuals with
similar phenotypes often have similar genotypes.

Question 35

individuals with similar phenotypes may mate because

Answer 35

a) phenotypic assortative mating occurs;
b) mating with relatives is preferred;
c) matings are primarily based on proximity

Question 36

inbreeding is a measure of

Answer 36

the probability that two alleles are identical by descent alleles descended from the same copy in a common ancestor ex Hemophilia in the Royal Families of Europe

Question 37

by “descent”

Answer 37

2 individuals come together w/ common ancestor, likely to share a gene from that ancestor and pass it on

Question 38

alleles identical by state

Answer 38

alleles that are the same in structure and function but are descended from two different copies in ancestors (nonrelated; 2 diff copies in ancestors)

Question 39

inbreeding depression

Answer 39

• incr appearance of lethal and deleterious traits with inbreeding
• inbreeding incr the % of homozygous individuals in the population
• need to bring in variation*

Question 40

outcrossing

Answer 40

is the avoidance of mating btwn related individuals

Question 41

which of the basic assumptions are violated when inbreeding occurs

Answer 41

• mating w/ themselves
• variation is lost
• inbreeding leads to homozygosity at almost all alleles

Question 42

as inbreeding increases, the avg yield of corn decreases, why?

Answer 42

no genetic variation = poor yield (genetic variation amongst all alleles lose robustness as become more universally homozygous)

Question 43

under what conditions can inbreeding be advantageous

Answer 43

• inbreeding can uncover (recessive) deleterious alleles; this can lead to the elimination (death of homozygotes) of these alleles in the population
• can keep together good combinations of genes that might be broken up by outcrossing

Question 44

what conditions might favor inbreeding

Answer 44

environment and individuals w/in it are stable; has a perfect set of genes that you do not want variation

Question 45

Two alleles are “identical by descent” if

Answer 45

(1) both are descended from the same allele in a common ancestor
or
(2) one allele is descended from the other

Question 46

The inbreeding coefficient of an individual

Answer 46

is the probability that its two gene copies at a locus are identical by descent