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CMMB Midterm 1 > Population genetics > Flashcards

Population genetics Flashcards

1
Q

population

A

clusters of people sharing common gene pool

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2
Q

populations characteristics

A

age structure
geography
birth and death rates
allele frequencies

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3
Q

population genetics

A

study of genetic variation and how gene/ geneotypes are maintained/ change in populations, not indicidual matings

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4
Q

population diversity

A

populations are more diverse than individuals

all alleles in a population are the gene pool

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5
Q

gene pool

A

set of genetic info carried by the members of a sexually reproducing population

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6
Q

allele frequency

A

frequency with which alternate forms of a particular gene are in the population
-freq of alleles in a population can change from generation to generation
chagne in alele frequency= change in phenotype frequency
-change in the gene pool= evolution in population

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7
Q

human genetic diversity

A

polymorphisms–> rep DNA seq variants that have a freq in the population of 1%<

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8
Q

how can allele freq be meaured in populations

A
  • sometimes allele frquencies can be meausred directly

- otherwise HW law has to be used to est allele freq with in populations

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9
Q

codominant allele frquency i

A

measured diresctly
both allleles are expressed
measured by counting the phenotype

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10
Q

recessive alle frequency

A

cant be measured directly

A/a= masked can count homo recessive

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10
Q

Hardy-Weinburg Law (equilibrium)

A

Relationship btw allele freq and genotype freq on a population

Allele and genotype freq is constant from generation to generation … Population meets certain assumptions

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11
Q

Resistance to human immunodeficiency virus

A

CCRS gene- receptor HIV uses to enter cell

Change in CCRS mutant recessive allele= HIV CANT ENTER RESSISTAN TO HIV

Homozygotes= resistant to HIV infection= lack of receptors

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12
Q

Assumptions HW law

A

1) population= big= no errors in measuring allele crews
2) all genotypes= equally reproduced

3) mating is random
4) no migration in/out of population
5) no new mutations
6) no motifs btw different generations
7) all matings produce same # offspring who are equally fertile

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13
Q

Equations

A

p+q=1

p=A
q=a

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

1=100% genotypes in new generation

p^2= AA 
q^2= aa

pq= Aa

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14
Q

Genetic equilibrium

A

Allele freq for a certain gene stays constant from generation to gen

Equilibrium in population explains why dominant alleles don’t replace recessive alleles

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15
Q

HW Law Human Genetics

A
  • Establish freq auto dom and recessive alleles in population
  • detect when allele frequency shifts in a population
  • measure frequency of heterozygous carriers of deleterious recessive alleles in a population
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16
Q

Calculate frequency of autosomal dominant and AutoSomal recessive alleles

A
  • Count frequency of individuals with recessive phenotype which is also homozygous recessive for aa
    -frequency genotype aa= q^2
    Solve for a

Freq of dominant allele A=p=1-q

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17
Q

Calculate frequency of alleles for X-linked traits

A

Female=2/3 of alleles

Males=1/3 of alleles

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18
Q

The number of males with the mutant phenotype =to the allele frequency for the recessive trait

A

Freq of x-linked train in males=q

Freq of trait in females is q^2

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19
Q

Frequency of heterozygotes

A

Disease causing alleles carried by heterozygotes
Frequency of heterozygous carrier= used to calculate the risk of having an affected child

Count homozygous (q^2) then calculate q

Calculate dominant allele p(p=1-q)

Calculate heterozygous=2pq

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20
Q

Factors that disturb Hardy Weinberg

A

1) nonrandom matings in humans
-associative mating
Consanguinity and inbreeding

2) founder effects
- population small number of individuals. (Founder) or drastic decrease I. Population (bottleneck)

3) genetic drift
- random flux of allele frequency from generation to generation (happens in small isolated populations)

Founder is a type of genetic drift

4) migration/gene flow
So diffusion of genrs across a barrier= merger of different gene population into larger populations results in a change in allele frequency

5) selection
Increase reproductive success of fitter genotypes

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21
Q

Natural selection

A

Acts on genetic diversity in populations and major driving force of evolution

22
Q

Fitness

A

Better adapted individuals result in increased chance of more offspring

23
Q

Heterozygote advantage

A

Increase freq of genetic disorders and some populations= do too selection= increased fitness

24
Q

Natural selection affects frequency of genetic disorders

A

Rare lethal or deleterious recessive alleles survive because many carried in heterozygous conditions

25
Q

Factors that affect distribution of alleles in human population

A

Migration
Founder effects
Mutations
Selection

26
Q

Lethal alleles

A

Duchene muscular dystrophy DMD die before reproducing
Mutation rate increases result in lots of DMD alleles
Frequency of DMD alleles in a population is often the balance between alleles introduced by mutation and that was removed by deaths

27
Q

Mutation generates

A

All new alleles but drift migration and selection deter the frequency of alleles in population

28
Q

Evidence for genetic contribution

A

Clustering of affected individuals and families
Risk of relatives = based on relatedness to affected individual
Shared phenotype can be due to a common environment

29
Q

Multifactorial inheritance

A

Single gene disease = predictable

Precise genotypes are unknown and environmental effects are variable

30
Q

Multifactorial inheritance the risk to relatives

A

Empiric risks: but you observed from data from families with an infected individual
ER specific for each multifactorial disease can change from population size /geographic area to another

31
Q

ER for MF traits

A

ER not calculated but is an observation population stat
ER is used to predict reoccurrence of the MF trait in a family
ER is affected by a number of factors

32
Q

MFI

A

Many factors involved in causing birth defects genetic and environmental factors combined genes from environmental factors and both parents

33
Q

ER birth defects

A 
Cleft palate 
Deafness
Club foot
Congenital heart 
Neural tube defect
34
Q

ER common diseases

A 
Asthma
Diabetes type one
Diabetes type two I blood-pressure
Rheumatoid arthritis 
Alzheimer's disease late onset above 60
Psoriasis
35
Q

Heritability of disorder

A

Proportion of liability given to genetic factors versus environmental factors

H2=100% traits=fully genetic
H2=0% traits= fully environmental

36
Q

Heritability of a traits equation

A 
# of relatives that share trait
-------------------------------------
# expected to share if trait 100% genetic

Heritability (H2)= variation (DZ-MZ)
———————
Variation DZ

DZ NOT EQUAL TO DZ= genetic and environment= MF

MZ=MZ THEREFORE GENETIC

MZ (100%)= 2xDZ(50%) MZ NOT = to MZ ENVIRONMENTAL DIFFERENCES

DZ=MZ ENVIRONMENT = if same environment any different= genetic factors

37
Q

Problems with heritability

A

Families share genetics and environment

38
Q

Separate genes from the environment

A

Adopted children
Compare birthparents to adopted parents
Sharing the environment only not genes

Twins
Compare monozygotic versus dizygotic twins
Difference in Twins = difference between amount of Genes shared environment is constant

39
Q

Twin studies

A

Monozygotic twins have the same genotype and equal environment
Dizygotic twins have a different Genotype and equal environment

40
Q

Concordance

A

If one twin is affected how often is the other affected?

41
Q

Concordance rates

A

-compare percent monozygotic twins concordant for traits versus percent of DZ TWINS concordant
If monozygotic twins are more concordant than differences are due to genetics

42
Q 
Autism= 90% MZ VS 2% DZ 
DEPRESSION = 46% MZ VS 9% DZ
A

Genetics

43
Q

MZ 80 DZ 16 disease is?

A

Genetic AR

44
Q

MZ 30 DZ 4 disease is?

A

Mutifactorial

45
Q

MZ 95 DZ 48 disease is?

A

Genetic AD

46
Q

MZ 7 DZ 7 disease is?

A

Environmental

47
Q

MZ 100 DZ 12.5 disease is?

A

Genetic xL Recessive males affected

48
Q

Sex ratio

A

Birth defects/ MF traits= difference in sex ratio

-risk to a relative increase if a proband is of a rarely where affected sex

49
Q

Quantitative traits

A

QT Loci: chromosomal regions associated with a complex trait present in individuals who have been affected

Q TL is right then one of the genes in this region should be directly involved in causing the trait

50
Q

Q TL mapping

A

1) complex treat that show strong genetic contribution
2) phenotype large group of individuals That have the same trait
3) genotype everyone

51
Q

Complexity of treat

A

More complex the trait harder it will be to identify QTL Or genes involved Need an increased number of individuals to have power to identify contributing Loci

52
Q

Heritability

A

Measure of the relative contribution of nature versus nurture

53
Q

Obesity

A

QL= obese overweight and normal
Quantitative= weight in pounds
MF= controlled by the environment
Controlled by genes protein that has an effect on appetite

CMMB Midterm 1 (6 decks)

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