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BB10007 Genetics > ✅Population Genetics - Paul Craze > Flashcards

✅Population Genetics - Paul Craze Flashcards

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Biology 101 flashcards
1
Q

What are alleles?

A

Alternative DNA sequences at a locus, inherited as a unit

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2
Q

What is a locus?

A

The position in the genome being considered

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3
Q

What are alleles caused by?

A

Single nucleotide polymorphisms and structural differences

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4
Q

What do alleles produce?

A

A genetically based phenotypic differences between individuals

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5
Q

When does a locus not contribute to variation?

A

When all individuals have the same allele

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6
Q

What does phenotypic variation contributed by a locus depend on?

A

The frequencies of alleles

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7
Q

How would the frequency of an allele be calculated?

A

Frequency = number of alleles/total

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8
Q

What are genetic markers?

A

Molecular variants used to differentiate between alleles

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9
Q

The frequency of heterozygotes in a population that is at Hardy-Weinberg equilibrium will…

A

…remain constant

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10
Q

How many alleles will a diploid population of N individuals have?

A

2N

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11
Q

How would the total number of A alleles be calculated?

A

2x number of AA homozygotes + number of Aa heterozygotes

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12
Q

What is evolution?

A

Change in allelic frequencies

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13
Q

What can population differences in allele frequencies be used to understand?

A

Gene flow/migration

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14
Q

How is a genotype frequency calculated?

A

Using the number of individuals with the genotype divided by the total number of individuals

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15
Q

What does the Hardy-Weinberg principle give?

A

The expected genotype frequencies in a model population

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16
Q

What are the Hardy-Weinberg assumptions?

A

Population is very large, random mating, no migration, no selection, no mutation

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17
Q

What is positive assortative mating?

A

Similar individuals tend to mate with each other

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18
Q

What is negative assortative mating?

A

Different individuals tend to mate with each other

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19
Q

What is inbreeding?

A

Individuals tend to mate with relatives

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20
Q

What are offspring of inbreeding more likely to have?

A

Two alleles that are identical by descent (IBD)

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21
Q

What does inbreeding increase?

A

Homozygosity

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22
Q

What is inbreeding measured by?

A

The inbreeding coefficient (F)

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23
Q

What is the inbreeding coefficient?

A

The probability that two alleles are IBD

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24
Q

Where does inbreeding occur most?

A

In self fertilising plant populations

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25
Q

What can inbreeding do to populations?

A

Decrease the fitness

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26
Q

What is genetic drift?

A

Random changes in allelic frequencies

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27
Q

What does Hardy-Weinberg tell you?

A

That there is no intrinsic force driving allelic change

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28
Q

What can changes in allelic frequencies be caused by?

A

Genetic drift, natural selection, migration

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29
Q

What is the expected error in allele frequencies samples in a population?

A

1/2N

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30
Q

What can happen to alleles in small populations?

A

They can be lost or fixed

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31
Q

What happens to alleles in large populations?

A

They can fluctuate

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32
Q

What are founder events?

A

When a new population is founded by very few individuals and the allele frequencies are different to the original population

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33
Q

What is natural selection based on?

A

The fact that different genotypes have different fitness

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34
Q

What is fitness?

A

The average contribution to the next generation made by an individual or that individual’s genome

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35
Q

What indicates greater fitness in terms of inheritance?

A

More copies into the next generation

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36
Q

How many alleles does selection favour?

A

One

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37
Q

What is gene flow?

A

Movement of alleles from one population to another

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38
Q

How does time taken to increase in frequency differ between alleles?

A

DOMINANT - initial increase rapid, but slows as it becomes more common
CODOMINANT - reaches fixation most rapidly
RECESSIVE - takes longer to increase but reaches fixation quickly once common

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39
Q

What factors can increase genetic variation within populations?

A

Mutation
Migration
Some types of natural selection

40
Q

What factors can decrease genetic variation within populations?

A

Genetic drift

Some types of natural selection

41
Q

What factors can increase genetic variation between populations?

A

Mutation
Genetic drift
Some types of natural selection

42
Q

What factors can decrease genetic variation between populations?

A

Migration

Some type of natural selection

43
Q

What are discontinuous trains?

A

Qualitative, can be categorised into a few classes

44
Q

What are continuous traits?

A

Quantitative, can vary along a scale of measurement

45
Q

What is polyphenism?

A

Some characteristics show normal distribution, others show bimodal distribution

46
Q

What are meristic traits?

A

Are determined by multiple genetic and environmental factors and can be measured in whole numbers. eg litter size

47
Q

What are threshold traits?

A

Are measured in presence or absence eg susceptibility to disease

48
Q

What kind of distribution is shown by the number of loci against the relative number of progeny?

A

Normal distribution

49
Q

What is phenotypic variance?

A

The total amount of variation among individuals in some trait, caused by underlying components of variation

50
Q

What are the components of phenotypic variation (Vp)?

A

Genetic variance (VG), environmental variance (VE), genotype-environment interaction variance (VGE)

51
Q

How is phenotypic variance calculated?

A

VG + VE + VGE

52
Q

What is the heritable variation?

A

Additive genetic variance (VA)

53
Q

What is the non-heritable variation?

A

Dominance genetic variance (VD), gene interaction (epistatic) variance (VI)

54
Q

How is Genetic variance calculated?

A

VA + VD + VI

55
Q

What is broad sense heritability?

A

The proportion of phenotypic variation attributable to genetic differences between individuals

56
Q

How is broad sense heritability calculated?

A

H^2 = VG/VP

57
Q

What is narrow sense heritablity?

A

The proportion of phenotypic variation that contributes to the resemblance between parents and offspring

58
Q

How is narrow sense heritability calculated?

A

h^2 = VA/VP

59
Q

What can heritability be measured by?

A

Regression, with a linear relationship between phenotype of offspring and phenotype of parents

60
Q

What is genotype-environment interaction?

A

When the difference between genotypes depends on the environment

61
Q

What can genetic correlations be down to?

A

Pleiotropy or linkage disequilibrium

62
Q

What is phenotypic correlation?

A

When the points in the correlation are different individuals

63
Q

What is genotypic correlation?

A

When the points in the correlation are different genotypes

64
Q

What is linkage disequilibrium?

A

When there is an association between alleles of different loci, eg if allele A tends to be found with allele B and a with b

65
Q

What is coupling linkage diequilibrium?

A

When the two dominant alleles associate, and so do the two recessive, eg AB and ab

66
Q

What is repulsion disequilibrium?

A

When one dominant allele associates with one recessive, eg Ab and aB

67
Q

What is pleiotropy?

A

Single locus can influence multiple traits at once, which are all inevitably correlated

68
Q

What does pleiotropy tend to result in?

A

Traits being inherited together

69
Q

What can evolution lead to over time in terms of lineages?

A

The splitting

70
Q

What is biological evolution?

A

Genetic (and potentially phenotypic) changes in a group of organisms

71
Q

What is anagenesis?

A

Evolution taking place in a single group (a lineage) with time

72
Q

What is cladogenesis?

A

Splitting of one lineage into two, new species arise

73
Q

What types of speciation does cladogenesis include?

A

Sympatric and allopatric

74
Q

What do species represent on the phylogenetic tree?

A

The smallest set of organisms that share a common ancestor and can be distinguished from other

75
Q

What is phylogeny?

A

A representation of the relationship between groups of organisms

76
Q

What is a rooted phylogenetic tree?

A

Uses distantly related species to infer ancestral state

77
Q

What is an unrooted phylogenetic tree?

A

No outgroup, relationship between lineages known but not ancestral

78
Q

What is allopatric speciation?

A

Speciation caused by geographical isolation

79
Q

What is peripatric speciation?

A

Speciation when a population is peripheral to the main one

80
Q

What is parapatric speciation?

A

Speciation when populations are not isolated, but adjoining, individuals mate locally

81
Q

What is sympatric speciation?

A

Describes speciation when populations overlap

82
Q

What are the two categories of reproductive isolating mechanisms?

A

Prezygotic and postzygotic

83
Q

What are examples of prezygotic isolating mechanisms?

A

Habitat isolation, behavioural isolation, sperm or pollen not transferred, temporal isolation

84
Q

What are examples of postzygotic isoation?

A

Zygote dies early in embryogenesis, F1 hybrids are inviable, F1 hybrids are sterile

85
Q

What is secondary contact?

A

Lineages may split over time but then migration or loss of barriers brings them back into contact

86
Q

What are genetic markers?

A

Some feature in the genome that allows us to differentiate between alleles

87
Q

What do genetic markers provide?

A

Information on genetic differences between individuals/populations

88
Q

What are genetic markers used in?

A

QTL and GWAS studies, forensics, genetic diversity

89
Q

What is RFLP?

A

Restriction fragment length polymorphism

90
Q

What was used before DNA technology to differentiate between populations?

A

Alloenzymes

91
Q

How is RFLP done?

A

Undegraded DNA is cut into fragments using restriction enzymes, and each fragment differs in length due to VNTRs

92
Q

What is RAD sequencing?

A

Cuts many short fragments and organises them into sequence stacks

93
Q

What are microsatellites?

A

Short tandem repeats, detected with PCR

94
Q

What is a haplotype?

A

A small chromosomal block inherited as a unit

95
Q

Why are mitochondrial markers important for population studies?

A

They have no recombination and uniparental inheritance so each sequence represents the end point of a linkage

96
Q

What can alleles be generated by?

A

Replication errors

BB10007 Genetics (3 decks)

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