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Exam study > Evo Devo > Flashcards

Evo Devo Flashcards

1
Q

Nucleotide =

A

sugar + phosphate + base

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2
Q

Pyrimidines

A

Cytosine and thymine

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3
Q

Purines

A

Adenine and guanine

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4
Q

Transcription

A

mRNA is transcribed from the DNA in the nucleus

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5
Q

Translation

A

Amino acid sequence is read off the mRNA sequence in the ribosomes

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6
Q

what percentage of DNA codes for genes?

A

5%

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7
Q

Uses of HWE

A

Simple conceptual model; estimation of variables; null hypothesis

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8
Q

what would cause a deviation from HWE

A

Non-random mating (assortative, disassortative or no mating)

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9
Q

Assortative mating

A

like genotypes preferentially mate; result is a deficit of heterozygotes

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10
Q

Disassortative mating

A

different genotypes preferentially mate; result is excess of heterozygotes

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11
Q

Forces of genetic change

A

natural selection, genetic drift, mutation and migration

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12
Q

response to natural selection is determined by variation in…

A

fitness

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13
Q

Fitness (w)

A

relative survival and reproductive success of a genotype

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14
Q

selection coefficient (s)

A

relative selective intensity against a genotype/reduction in fitness relative to the best genotype (1-w)

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15
Q

Balance of selection and mutation

A

selection can never eliminate deleterious alleles because they keep re-appearing by mutation

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16
Q

why do chromosome heterozygotes have higher fitness

A

Dominance: Chromosomal heterozygotes mask deleterious recessives at many loci

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17
Q

example of single locus heterozygote advantage

A

Sickle cell anemia polymorphism in humans (anemia selects against SS, malaria selects against AA)

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18
Q

Why are there not many examples of single locus heterozygote advantage

A

not common; hard to detect; theoretical problem of genetic load

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19
Q

positive frequency dependence

A

fitness increases with frequency, results in monomorphism

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20
Q

negative frequency dependence

A

fitness decreases with frequency, result is polymorphism

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21
Q

examples of negative frequency dependence

A

predation, mate choice, niche variation

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22
Q

causes of genetic drift

A

mendelian segregation, finite population size

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23
Q

principles of genetic drift

A
  • The direction of genetic drift in unpredictable
  • The magnitude of genetic drift depends on population size
  • The long-term effect is to reduce variation within a population
  • Genetic drift causes populations to diverge from one another
  • causes heterozygosity to decrease over time
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24
Q

factors that affect effective population size

A

unequal sex ratio; variation in population size; variation in family size; mitochondrial DNA

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25
Q

founder effect

A

Establishment of a new population by a few original founders

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26
Q

population bottleneck

A

population is suddenly reduced in size

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27
Q

identical by state

A

functionally equivalent alleles

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28
Q

identical by descent

A

pairs of alleles that trace to the same copy

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29
Q

inbreeding coefficient (F)

A

probability that two copies of a gene are identical by descent

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30
Q

effective population size (Ne)

A

the number that when substituted for N in equations based on ideal populations, describes the drift experienced by the actual population

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31
Q

what is mutation

A

any heritable change in genetic material

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32
Q

types of mutation

A

chromosomal; point; indels; gene duplications

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33
Q

chromosomal mutations

A
  • Change in the number or structure of chromosomes
  • Aneuploidy – extra or missing chromosomes
  • Polyploidy – entire sets of chromosomes duplicates
  • Inversions – chromosome breaks and is flipped 180 degrees
  • Translocations – chromosome breaks and attaches to a non-homologous chromosome
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34
Q

point mutations

A

A change in a single nucleotide in a DNA sequence

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35
Q

Indels

A

Insertions or deletions in the DNA sequence caused by errors in DNA replication

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36
Q

Gene duplication

A

New copies of a gene or groups of genes

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37
Q

why does sexual reproduction exist

A

theories
- genetic constraint
- sex can accelerate evolution
- coevolution of hosts and parasites
- mutational theory

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38
Q

genetic constraint

A

Mutations to produce asexual reproduction have not occurred so we are ‘stuck with it’ (unlikely because mutation for asexual reproduction is not difficult, it has arisen many times)

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39
Q

coevolution of hosts and parasites

A
  • Sex likely to be advantageous in changing environments
  • Coevolution between hosts and parasites can generate rapid ‘environmental’ change
  • Arms race between hosts resistance mechanism and parasites method of penetrating defences
40
Q

sex can accelerate evolution

A

Beneficial mutation, at separate loci, can be combined in a single individual faster with sex

41
Q

mutational theory

A

Sex exists because it enhances the power of selection against deleterious mutation

42
Q

inbreeding

A

positive assortative mating for relatedness; mating between related individuals

43
Q

how does inbreeding differ from assortative mating

A

it affects all genes, not just those controlling that trait which mating preference is based

44
Q

what does inbreeding result in

A

excess of homozygotes and deficiency of heterozygotes

45
Q

autozygous

A

Alleles that are ibd are derived by replication from a single allele

46
Q

allozygous

A

Alleles that are not ibd are called

47
Q

Inbreeding depression

A

increased appearance of lethal and deleterious traits with inbreeding

48
Q

Does inbreeding ‘purge’ deleterious recessive alleles?

A

If deleterious recessives are responsible for inbreeding depression, then populations that habitually inbred should have higher frequencies of fitter wild-type alleles

49
Q

population subdivision

A

Most populations are grouped into smaller subpopulations where random mating usually occurs (genetic neighbourhood)

50
Q

reduction in heterozygosity due to population subdivision

A

wahlund effect

51
Q

why is it important to know F statistic for conserving genetic variation

A
  • When a population has no population structure (FST close or equal to 0), there is no variation in allele frequencies between subpopulations, therefore genetic resources can be conserved by protecting one or two large populations
  • If FST is large, there is a high population structure and most genetic variation exists between subpopulations rather than within subpopulations, in these species it is necessary to protect as many subpopulations as possible to conserve genetic diversity
52
Q

gene flow

A

The movement of genes between subpopulations within a species

53
Q

Homogenising force

A

holds the gene pools of subpopulations together and limits how much genetic divergence takes place

54
Q

genetic variation has two impacts on island populations:

A
  • Reduces genetic variation within populations
  • Increases genetic variation between populations
55
Q

stepping stone model

A

Recognizes that gene flow is likely to be greater among demes (populations) closer together

56
Q

polygenic

A

traits that are controlled by multiple genes (e.g. height)

57
Q

coadaptation

A

allele favoured by selection if it is in the same individual as a particular allele at another locus

58
Q

haplotype

A

combinations of alleles at different loci

59
Q

linkage equilibrium

A

When alleles at different loci combine independently

60
Q

linkage disequilibrium

A

when haplotype frequencies deviate from linkage equilibrium

61
Q

recombination frequency

A

the frequency of recombination between two loci (range 0-0.5)

62
Q

significance of linkage equilibrium

A
  • Simplest model for 2 loci (HWE for single locus)
  • Deviations can indicate that something interesting is happening (i.e. one of the assumptions is not met)
  • Lets us know if more complex two-locus theory is needed
63
Q

causes of linkage disequilibrium

A

linkage; genetic drift; non-random mating; mutation; natural selection

64
Q

linkage disequilibrium mapping

A

Associations between traits and molecular markers are used to identify genes controlling traits

65
Q

species concepts

A

biological; recognition; ecological; phenetic; phylogenetic

66
Q

biological species concept

A

Groups of interbreeding natural populations that are reproductively isolated from other groups (no gene flow)

67
Q

recognition species concept

A

Group of individuals with shared specific mate recognition systems

68
Q

ecological species concept

A

Defines a species as a set of individuals with shared ecological attributes

69
Q

phenetic species concept

A

Defines a species as a set of individuals with shared morphological attributes

70
Q

phylogenetic species concept

A

Species are identified by estimating the phylogeny of closely related populations and finding the smallest monophyletic group

71
Q

what stops species interbreeding

A

Reproductive isolating barrier (pre or post zygotic) are evolved characters that prevent interbreeding between species

72
Q

how does reproductive isolation evolve?

A
  • allopatric speciation model (geographical isolation)
  • sympatric speciation model
73
Q

genetic correlation can exist for two reasons:

A
  • Pleiotrophy – one gene influences more than one trait
  • Hitch-hiking – natural selection favours one locus, genes at other loci also increase
74
Q

qualitative vs quantitative traits

A
  • qualitative: discrete categories
  • quantitative: needs to be measured
75
Q

quantitative traits

A

Depend on genes whose individual effects are small in relation to variation attributed to other causes

76
Q

common property of quantitative traits

A

sibling resemblance (generally, the closer the relationship, the closer the resemblance)

77
Q

breeder’s equation

A
  • Proportion of total phenotypic variance that is due to genetic causes
78
Q

method for quantifying resemblance between parents and offspring

A

parent-offspring regression

79
Q

paternal half siblings

A

A powerful method for testing for additive genetic effects based on the covariance among paternal half siblings

80
Q

basic principle of paternal half siblings

A

where males provide no resources at reproduction other than genes, and phenotypic similarity among his offspring from different females must be due to those offspring sharing the same paternal genes

81
Q

the fitness function

A

Describes the strength and form of selection acting on the phenotype

82
Q

direct selection

A

causal relationship between relative fitness and phenotype

83
Q

indirect selection

A

when there is a correlation between the focal trait and another one that experiences direct selection

84
Q

correlational selection

A

When two traits interact to determine fitness

85
Q

applications of quantitative genetics in the wild

A

medicine; conservation; selective breeding; disease resistance

86
Q

additive genetic variation

A

the variation that causes offspring to resemble their parents

87
Q

allelic diversity

A

the variation discernable through molecular genetic techniques

88
Q

fisher’s fundamental theorem

A
  • at each generation, only a subset of fitness related alleles pass on to the next generation
  • There should be very little genetic variation for traits that are closely related to fitness
89
Q

mutation:selection balance

A

Selection and drift must be balanced by mutation and other mechanisms that maintain genetic variation

90
Q

whether mutations can supply enough genetic variation depends on:

A
  • the genomic mutation rate
  • the intensity of selection
  • the number of genes involved
91
Q

how can variation be maintained in variable environments

A

When generations overlap or environmental heterogeneity is spatial, genetic variation can be maintained by migration between the ‘patches’

92
Q

disruptive selection

A
  • Short term increases in heritability
  • Practice: natural selection
93
Q

theory of selection for heterozygotes

A
  • where the optimum phenotype is the heterozygote
  • Practice: mate choice in Antarctic fur seals
94
Q

theory of frequency dependent selection

A
  • rare genotypes have higher fitness than common ones, creating ‘negative’ frequency dependent selection
  • Practice: frequency dependent selection on male phenotype in a species of guppy
95
Q

theory of antagonistic pleiotrophy

A
  • Genes that enhance the fitness pay-off from one aspect of life-history reduce the pay-off from another
  • Practice: attractiveness and male survival in the guppy
96
Q
A

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