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BIOL 2400 > Before midterm 2 > Flashcards

Before midterm 2 Flashcards

1
Q

What is quantitative genetics?

A

The study of genetic mechanisms of continuous phenotypic traits

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2
Q

Describe polygenetic

A
  • influenced by many gene loci
  • additive effects among alleles
  • dominant/recessive effects among alleles
  • interactions between loci
  • interactions with the environment
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3
Q

what is epistasis?

A

interactions between loci

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4
Q

what is phenotypic plasticity?

A

interactions of alleles with the environment

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5
Q

Is the phenotypic difference among individuals usually quantitative or qualitative?

A

quantitative

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6
Q

What is variance?

A

a statistically measure of the dispersion of trait values about their mean
- additive

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7
Q

describe polygenetic inheritance

A

each locus has either a positive or negative effect

- trait value is simply the sum of all the values of each allele and all loci

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8
Q

describe quantitative traits

A
  • influenced by many loci each with a small effect
  • experience both genetic and environmental variations
  • can’t easily determine genotype by phenotype
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9
Q

what does Vp stand for?

A

total variance in phenotypic trait in a population

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10
Q

what does Vg stand for?

A

genetic difference among individuals

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11
Q

what does Ve stand for?

A

environmental conditions in which the individual develops

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12
Q

What does Vp =?

A

Vp = Vg + Ve

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13
Q

what is broad sense heritability?

A

the proportion of total phenotypic variation that is due to genetic variation

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14
Q

what is the equation for broad sense heritability?

A

H^2 = Vg/Vp

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15
Q

what is the problem with broad sense heritability?

A

represents all genetic variance as a single value

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16
Q

what does Va stand for?

A

additive genetic variance

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17
Q

what does Vd stand for?

A

variance due to dominance effects of the alleles

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18
Q

what does Vi stand for?

A

variance attributable to epistatic interactions among alleles at various genetic loci

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19
Q

what does Vg =?

A

Vg = Va + Vd + Vi

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20
Q

what is narrow sense heritability?

A

the proportion of total phenotypic variation that is due to additive genetic variation

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21
Q

what is the equation for narrow sense heritability?

A

h^2 = Va/Vp

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22
Q

what is narrow sense heritability used to predict?

A

the response to selection

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23
Q

what happens when components of variation act independently?

A

their effects are additive

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24
Q

what does high heritability not prevent?

A

environmental changes from having a big effect

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25
Q

what does low heritability not prevent?

A

mutations from having a large effect

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26
Q

when does h^2 = 0?

A

when phenotypic variation is due solely to environmental factors

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27
Q

when does h^2 = 1?

A

when phenotypic variation is due to allelic differences

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28
Q

what is directional selection

A

when smaller or larger traits are favoured (one not both)

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29
Q

what is stabilizing selection?

A

when intermediate values are favoured

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30
Q

what id disruptive selection?

A

when extreme values are favoured

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31
Q

what is selection differential?

A

the difference in trait means before and after selection takes place

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32
Q

what is the equation for selection differential?

A

S = mean(after) - mean (before)

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33
Q

what is the selection breeder’s equation?

A

R = h^2 S

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34
Q

what does R stand for?

A

the evolutionary response to selection (change in phenotype between parent and offspring)

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35
Q

what does S represent?

A

the phenotypic variation that influences fitness

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36
Q

What can happen if selection is strong?

A

a population can respond to a trait even if it is only weakly heritable

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37
Q

what can happen if a trait’s heritability is high?

A

even weak selection can lead to evolutionary change

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38
Q

when does the most rapid evolutionary responses occur?

A

when both heritability and selection are strong

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39
Q

what is the quantitative trait locus (QTL)?

A

the chromosomal region with effects on the trait

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40
Q

are evolution and selection the same?

A

no

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41
Q

what does the magnitude of evolutionary change depend on?

A

strength of selection

heritability

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42
Q

what can selection occur without evolution?

A

when h^2 = 0

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43
Q

what is the neutral theory?

A

The majority variation at molecular level has no affect on survival and reproduction. Frequency of most alleles is determined by Genetic Drift

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44
Q

what did Motoo Kimura and colleagues describe in 1968 and 1969?

A

several observations that do notsupport the hypothesis that NS is responsible for most genetic variation within and between species

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45
Q

what observations lead to the neutral theory?

A

1 . Levels of polymorphism at allozyme loci within species are too high to be maintained primarily by natural selection.

  1. The rate of protein evolution is too high to be caused by natural selection. Rates of DNA evolution are even higher.
  2. Proteins seem to evolve at a constant rate over time.
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46
Q

describe Kimura’s neutral theory

A
  1. the vast majority of mutations that become fixed in population are neutral with respect to fitness.
  2. Genetic drift, not selection, dominates evolution at molecular level.
  3. The rate at which new neutral mutants become fixed equals the mutation rate (μ, mutation per gene per gamete)
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47
Q

what are 2 surprising conclusions regarding neutral theory for genetic drift?

A
  1. No positive selection (there is negative selection/purifying selection)
  2. The rate of fixation of novel alleles (substitution) due to drift does not depend on population size
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48
Q

what does μ represent?

A

mutation rate

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49
Q

in every generation how many new alleles are there?

A

2N μ

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50
Q

what is the chance that every allele in a population has to become fixed?

A

1/(2N)

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51
Q

what is the probability of a new mutation occurring, and going to fixation by genetic drift alone?

A

1/(2N)x[2N μ]= μ

52
Q

what is the average time to fixation of a neutral allele by genetic drift?

A

4Ne generations

53
Q

how long may Neutral polymorphism persist in a population?

A

a very long time causing high levels of protein and DNA polymorphism that we actually observe

54
Q

what are majority of protein evolution mutations?

A

neutral, fixed in population by drift

55
Q

how are Advantageous mutations fixed in populations?

A

by natural selection - rare

56
Q

what is the probability of a new mutation occurring and going to fixation by GD alone?

A

1/(2N) x 2N x μ= μ

57
Q

what happens if μ remains fairly constant over time?

A

the rate of allele substitution per gene per generation will also remain fairly constant

58
Q

what does natural selection do to the frequency of deleterious mutations?

A

decreases it

59
Q

deleterious mutations have what kind of impact on the observed rate of allele substitution?

A

little

60
Q

what are the predictions of neutral theory?

A
  1. There is an inverse correlation between the rate of substitution and the degree of functional constraints on a gene
  2. There is a constant rate of sequence substitution–molecular clock
61
Q

what is more common in protein coding genes; synonymous or non-synonymous?

A

synonymous

62
Q

what is Pseudogenes?

A

highest divergence rate

63
Q

according to neutral theory, what dominates molecular evolution?

A

drift

64
Q

what is a hermaphrodite?

A

an organism that has complete or partial reproductive organs and produces gametes normally associated with both male and female sexes

65
Q

what does the production of males lead to?

A

twofold cost of sex

66
Q

what are the benefits of sex?

A
  • results in more genetic variation (faster evolution)
  • can recombine beneficial mutations
  • can clear deleterious mutations
67
Q

what is Muller’s Ratchet?

A

The process by which asexual genomes accumulate deleterious mutations

68
Q

what is the Red Queen effect?

A

Biological arms race: between hosts and parasites

69
Q

what are the costs of sex?

A
  • two fold cost of sex
  • Search costs to find a mate
  • Reduced relationship with offspring
  • Risk of sexually transmitted disease
70
Q

how do Bdelloid rotifers compensate for the lack of sex?

A
  • Metabolic dormancy and dehydration under harsh conditions
  • Avoid parasite and disease during desiccation
  • As desiccate and rehydrate, membranes rupture –ingest foreign DNA
  • Horizontal gene transfer from bacteria, fungi and plants –import genes
71
Q

what type of environment favours sex?

A

unstable

72
Q

what kind of environment favours asexual reproduction?

A

stable

73
Q

The spiny water flea(Bythotrephes longimanus)reproduces asexually through most of the summer and fall and then engages in one round of sexual reproduction at the end of the season.Which of the following is a reasonable explanation for why they switch to sexual reproduction in the fall?
A.Muller’s Ratchet -mutations have accumulated over the summer
B.Increase genetic variation to cope with a change in the environment the next spring
C.Its too hot to make sperm in the summer
D.To bring up their numbers in fall so they don’t go extinct

A

B.Increase genetic variation to cope with a change in the environment the next spring

74
Q

what is sex?

A

is the combining and mixing of chromosomes during reproduction (=meiosis and recombination)

75
Q

what is parthenogenesis?

A

a mode of reproduction in which female sex cells undergo meiosis but are not fertilized by sperm
- produce only daughters

76
Q

what is fecundity?

A

the reproductive capacity of an individual

77
Q

what is anisogamy?

A

sexual reproduction involving the fusion 2 dissimilar gametes

78
Q

what is sexual selection?

A

differential reproductive success due to variation in success at getting mates

79
Q

what is the operational sex ratio (OSR)?

A

the ratio of male to female individuals who are available for reproducing at a given time

80
Q

what are females limited by when it comes to sex?

A

of eggs

81
Q

what are males limited by when it comes to sex?

A

of mates

82
Q

what is intrasexual selection?

A

male-male competition

83
Q

what is intersexual selection?

A

female choice

84
Q

The male collared flycatcher has distinct black and white plumage while the female is more boring in colour. Which sex do you expect has the greater variance in reproductive success?
A.Male
B.Female
C.Variance in reproductive success is always equal

A

A.Male

85
Q

The size of the white forehead patch on male collared flycatchers is a sexually selected trait. Do you expect that the size of the patch increases male mating success through intrasexual or intersexual selection?

A

intersexual selection

86
Q

what is a Preexisting Sensory Bias in females?

A
  • Females have a sensory system for avoiding predators and finding food
  • Female preference for shapes and colours evolved first
  • Male traits evolve to match female preferences
87
Q

what are sexy-sons?

A
  • Once a female preference is common these will be reinforced
  • Females choosing preferred mates will produce sons that are preferred -if male trait is heritable
  • Preference and male display are reinforced
  • indirect benefit
88
Q

Female swordtail fish prefer males with longer swords (lower lobe of caudal fins). Suppose that females receive no resources(e.g.nuptial gifts etc.) from males, and that offspring of males with longer swords do not survive better than offspring from males with short swords. What hypothesis might explain the wide spread female preference for males with longer swords?
A.Direct benefits
B.Sexy-sons
C.Good gene

A

B.Sexy-sons

89
Q

what is polyandry?

A

females mating multiple times

90
Q

what are advantages of polyandry?

A
  1. males may be sterile or temporarily out of sperm
  2. maximize offspring genetic diversity, avoid genetic incompatibility and inbreeding.
  3. Protection against infanticide
  4. More food or resources
91
Q

what is the dilution effect?

A

safety in numbers that arises through swamping the foraging capacity of local predators

92
Q

what are the costs of group living?

A
  • Increased conspicuousness to predators
  • Increased competition for food
  • Increased competition for mates
  • Decreased certainty of paternity/ maternity
  • Increased transmission of disease/ parasites
93
Q

what are the benefits of group living?

A
  • Increased vigilance
  • Dilution effect
  • Enhanced defence capability
  • Cooperative foraging / hunting
  • Improved defence of critical resources
94
Q

what is altruism?

A

The actor incurs a cost and the recipient benefits in terms of surviving offspring

95
Q

what is the Group selection –v1.0 hypothesis?

A

Traits can evolve that are costly to the individual as long as they benefit the group

96
Q

what are the problems with group selection?

A
  • Natural selection does not favour selflessness
  • Population of altruists could be “infiltrated” via mutation or gene flow by a cheater who behaved selfishly
  • Cheater genes would spread rapidly because they would leave more offspring, eventually replacing the altruists
97
Q

what is the kin selection hypothesis?

A

Traits can evolve that are costly to the individual as long as they benefit kin (relatives)

98
Q

what is inclusive fitness?

A

inclusive fitness = Direct fitness + Indirect fitness

99
Q

what is direct fitness?

A

personal reproductive success

100
Q

what is indirect fitness?

A

weighted reproductive success of genetic relative

101
Q

what does indirect fitness depend on?

A

coefficient of relatedness, r

102
Q

when does an altruistic allele increases in frequency by Hamilton’s rule?

A

Br> C

103
Q

what is the green beard hypothesis?

A

Traits can evolve that are costly to the individual if they help unrelated individuals with signals linked to altruistic behaviour
- effect can lead to evolution of altruism in unrelated individuals

104
Q

what is the Reciprocal altruism hypothesis?

A

Traits can evolve that are costly to the individual as long as individuals are likely to be reciprocated

105
Q

what does w stand for?

A

probability that a selfless behaviour will be reciprocated`

106
Q

what is the formula for when altruistic behaviour will evolve?

A

wb-c > 0

107
Q

what is game theory?

A

a mathematical approach to studying behaviour that solves for optimal decisions in strategic situations where the payoff to a particular choice depends on the choice of others

108
Q

what is evolutionary stable strategy?

A

a behaviour that, if adopted by a population in a given environment, cannot be invaded by any alternative behaviour

109
Q

what is an organisms life history?

A

their scheduleof reproduction and survival

110
Q

what are life history traits closely related to?

A

fitness

111
Q

what are the ideal life history traits for sexual maturity, producing offspring, and lifespan?

A

at birth, continuously in large numbers, and live forever

112
Q

what does no species have ideal life history traits?

A

energetic constraints

113
Q

what are the fundamental trade offs?

A
  • Reproduction and survival (growth)
  • Current and future reproduction
  • Offspring number and size
114
Q

what is natural selection expected to do in terms of life history?

A

Maximize number of offspring surviving to maturity, which Depends on likelihood of survival to different age classes

115
Q

what are the 2 hypotheses related to evolutionary theory of aging?

A
  1. The mutations accumulation hypothesis

2. The antagonistic pleiotropy hypothesis

116
Q

what does RS represent?

A

reproductive success

117
Q

is natural selection weaker at beginning or end of life?

A

end of life

118
Q

what may increase RS?

A

A mutation causing earlier reproduction and earlier death

119
Q

when do tradeoffs arise?

A

investment in one trait results in lower investment in another trait due to energy constraints

120
Q

what does lower likelihood of survival encourage?

A

earlier reproduction, larger number and smaller size of progeny

121
Q

what is the Trivers-Willard hypothesis?

A

Mothers alter sex ratio depending on condition

  • Produce females when mother in poor conditions
  • Produce males when mother in good condition
122
Q

what is the mother hypothesis?

A

risk of reproduction at older age selects for reduced fertility

123
Q

what is the grandmother hypothesis?

A

loss of fertility associated with shift in investment to grandchildren

124
Q

how can family conflict often be explained?

A

indirect benefits

125
Q

what types of family conflict are there?

A

parental conflict
parent-offspring conflict
offspring-offspring conflict

126
Q

when should a mother stop feeding the baby?

A

benefit (to offspring) > cost (to parent)

benefit/cost > 1

BIOL 2400 (3 decks)

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