Population Genetics

Question 1

polymorphic human DNA sequence

Answer 1

for any gene there are many different specific versions of that gene’s sequence in the population

Question 2

allele

Answer 2

each different version o the gene’s sequence

Question 3

isoform

Answer 3

version of the protein that has a significantly higher or lower level of activity than the isoform made by most other people

Question 4

genotype

Answer 4

combination of gene alleles you posses for a given gene

Question 5

heterozygous genotype

Answer 5

you have different versions of the gene’s sequence (2 different alleles) in your 2 copies of the gene

Question 6

homozygous genotype

Answer 6

you have same version of gene’s sequence (2 copies of the same allele) in your two copies of the gene

Question 7

phenotype

Answer 7

your observable traits (physical traits, personality, biochemical parameters, susceptibility to specific diseases, response to specific drugs)

Question 8

population

Answer 8

group of individuals that reproduce sexually and interbreed within that population

Question 9

the population’s gene pool

Answer 9

all the different gene alleles that are present in the population

Question 10

allele frequency

Answer 10

of alleles of the type

Question 11

formula for X-linked allele in female-only population

Answer 11

f(A) = [f(AA) x 1] + [f(Aa)/2]

Question 12

genotype frequency

Answer 12

of people w the genotype in question/total number of people (which is the same as the total # of genotypes)

Question 13

X linked genes

Answer 13

a woman has 2 alleles per gene and a man has one (hemizygous) but both have only one genotype

Question 14

Y linked genes

Answer 14

only males have a genotype which contains only one allele per gene (hemizygous)

Question 15

changing allele frequencies and genotype frequencies

Answer 15

unrelated outsiders migrating into population, nonrandom mating w/i a population, gene mutations, specific gene alleles being favored by chance, natural selection, groups being forced to flee their homes by war or natural disasters

Question 16

Hardy-Weinberg Equilibrium

Answer 16

(1) under certain circumstances frequency of all gene alleles w/i population will stabilize (2) when something changes the frequency of distribution of alleles in a population after one generation of random mating you can predict frequency of homozygous and heterozygous genotypes in population if you know frequencies of the specific alleles in questions (3) p^2 + 2pq + q^2 = 1

Question 17

p

Answer 17

frequency of A allele

Question 18

q

Answer 18

frequency of a allele

Question 19

frequency of AA

Answer 19

p^2

Question 20

frequency of Aa

Answer 20

2pq

Question 21

frequency of aa

Answer 21

q^2

Question 22

HW for 3 alleles

Answer 22

p^2 + q^2 + r^2 + 2pq + 2pr +2qr = 1

Question 23

HW assumptions

Answer 23

population is large, population mates randomly w/i itself (no artificial selection), no migration into population by outsiders, no genetic mutations, no gene alleles get favored by change, no advantage/disadvantage in terms of genetic fitness in having one allele/genotype or another of a given gene

Question 24

gene w frequencies not in HWE

Answer 24

many mean there is something interesting about that gene/allele/genotype; ex: one allele/genotype increases or decreases a person’s risk for disease or otherwise increases/decreases genetic fitness in that environment

Question 25

evolution & HWE

Answer 25

population can’t evolve if in HWE bc its allele frequencies/genotype frequencies will never change; sexual reproduction maintains genetic diversity but can’t power evolution bc it doesn’t cause allele/genotype frequencies to change: it take mutation, migrations, selection or chance to drive evolution

Question 26

1 - q =

Answer 26

p

Question 27

degrees of freedom

Answer 27

of possible different genotypes - # of different alleles for that gene; use Chi square test to test whether a population is in HWE or not (gene w 2 alleles df = 1)

Question 28

Chi Square Test Formula

Answer 28

(sigma: (O-E)^2)/expected

Question 29

genetic drift

Answer 29

possibility that gametes that made next generation just happened to have disproportionate # the possess one particular allele of a gene; smaller pop = genetic drift is more likely (sampling error is greatest when population is small)

Question 30

genetic bottleneck

Answer 30

small sample of population gets isolated (or survives a war) and makes up the original gene pool for the subsequent population; causes genetic drift; allele frequencies in this group will be determined by who survived the war there was no natural selection involved

Question 31

founder effect

Answer 31

caused by genetic bottleneck; original gene pool of the population was very limited in its diversity

Question 32

effects of genetic drift

Answer 32

inc frequency of some alleles and dec that of others; reduces genetic variability w/i population some alleles will become fixed (present at 100% freq); causes diff population to become more different from each other over time

Question 33

natural selection

Answer 33

phenotypic traits that allow ind to thrive relative to his/her peers in that given environment

Question 34

genetic fitness

Answer 34

ability to reproduce relative to contemporaries; symbolized as W ranges from 0 to 1.0

Question 35

overdominance

Answer 35

heterozygotes have greater fitness than homozygotes; maintains the freq of both alleles

Question 36

underdominance

Answer 36

heterozygotes have lower fitness than homozygotes; directional selection occurs, where one allele’s freq increases more than the other’s

Question 37

selection coefficient (s)

Answer 37

reflects how severely a selection method works against a given genotype; s = 1 - W

Question 38

formula for effect of natural selection on genotypes in next generation

Answer 38

(p^2W11)/wbarr

Question 39

X linked gene

Answer 39

HW only applies for females and not males

Question 40

direction selection

Answer 40

most favored allele will eventually get fixed at freq of 1.0; if heterozygous genotype has lowest fitness

Question 41

recessive disease allleles

Answer 41

removed very slowly from population

Question 42

negative eugenics

Answer 42

actively reducing freq of “bad” alleles (ex: sterilized handicapped people)

Question 43

postive eugenics

Answer 43

actively encouraging propagation of “good” alleles (ex: selective mating, sperm and egg banks)

Question 44

selective mating

Answer 44

you select your mates on the basis of some characteristics you think are important

Question 45

negative eugenics & ethical standards

Answer 45

sterilize unaffected parents w 3/4 chance of unaffected child, unaffected relatives

Question 46

positive assortative mating

Answer 46

mating w people who have characteristics similar to yours; nonrandom mating

Question 47

negative assortative mating

Answer 47

mating w people who have characteristics different from yours; nonrandom mating

Question 48

assortative mating

Answer 48

choosing people based on their phenotypes; only affects allele frequencies of genes that influence those traits and genes that are linked to those genes

Question 49

inbreeding

Answer 49

positive assortative mating for relatedness; affects all genes’ alleles; increases proportion of homozygotes; - increase in freq of genetic disorders bc recessive mutations come out more

Question 50

inbreeding coefficient (F)

Answer 50

proportion of ind’s homozygous genotypes in which 2 alleles are derived from common ancestor; range from 0 to 1.0; reduced by 2Fpq increases by Fpq

Question 51

gene mutations

Answer 51

eventually rate of forward and reverse mutations equalizes; u = forward rate v = reverse rate equi = q = u/(u+v)

Question 52

effects of migration

Answer 52

freq changes by m(q1-q2)