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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
Natural selection affects frequency of genetic disorders
Rare lethal or deleterious recessive alleles survive because many carried in heterozygous conditions
25
Factors that affect distribution of alleles in human population
Migration Founder effects Mutations Selection
26
Lethal alleles
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
Mutation generates
All new alleles but drift migration and selection deter the frequency of alleles in population
28
Evidence for genetic contribution
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
Multifactorial inheritance
Single gene disease = predictable | Precise genotypes are unknown and environmental effects are variable
30
Multifactorial inheritance the risk to relatives
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
ER for MF traits
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
MFI
Many factors involved in causing birth defects genetic and environmental factors combined genes from environmental factors and both parents
33
ER birth defects
``` Cleft palate Deafness Club foot Congenital heart Neural tube defect ```
34
ER common diseases
``` Asthma Diabetes type one Diabetes type two I blood-pressure Rheumatoid arthritis Alzheimer's disease late onset above 60 Psoriasis ```
35
Heritability of disorder
Proportion of liability given to genetic factors versus environmental factors H2=100% traits=fully genetic H2=0% traits= fully environmental
36
Heritability of a traits equation
``` # 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
Problems with heritability
Families share genetics and environment
38
Separate genes from the environment
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
Twin studies
Monozygotic twins have the same genotype and equal environment Dizygotic twins have a different Genotype and equal environment
40
Concordance
If one twin is affected how often is the other affected?
41
Concordance rates
-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
``` Autism= 90% MZ VS 2% DZ DEPRESSION = 46% MZ VS 9% DZ ```
Genetics
43
MZ 80 DZ 16 disease is?
Genetic AR
44
MZ 30 DZ 4 disease is?
Mutifactorial
45
MZ 95 DZ 48 disease is?
Genetic AD
46
MZ 7 DZ 7 disease is?
Environmental
47
MZ 100 DZ 12.5 disease is?
Genetic xL Recessive males affected
48
Sex ratio
Birth defects/ MF traits= difference in sex ratio | -risk to a relative increase if a proband is of a rarely where affected sex
49
Quantitative traits
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 TL mapping
1) complex treat that show strong genetic contribution 2) phenotype large group of individuals That have the same trait 3) genotype everyone
51
Complexity of treat
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
Heritability
Measure of the relative contribution of nature versus nurture
53
Obesity
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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