Before midterm 2 Flashcards
(126 cards)
1
Q
What is quantitative genetics?
A
The study of genetic mechanisms of continuous phenotypic traits
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
3
Q
what is epistasis?
A
interactions between loci
4
Q
what is phenotypic plasticity?
A
interactions of alleles with the environment
5
Q
Is the phenotypic difference among individuals usually quantitative or qualitative?
A
quantitative
6
Q
What is variance?
A
a statistically measure of the dispersion of trait values about their mean
- additive
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
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
9
Q
what does Vp stand for?
A
total variance in phenotypic trait in a population
10
Q
what does Vg stand for?
A
genetic difference among individuals
11
Q
what does Ve stand for?
A
environmental conditions in which the individual develops
12
Q
What does Vp =?
A
Vp = Vg + Ve
13
Q
what is broad sense heritability?
A
the proportion of total phenotypic variation that is due to genetic variation
14
Q
what is the equation for broad sense heritability?
A
H^2 = Vg/Vp
15
Q
what is the problem with broad sense heritability?
A
represents all genetic variance as a single value
16
Q
what does Va stand for?
A
additive genetic variance
17
Q
what does Vd stand for?
A
variance due to dominance effects of the alleles
18
Q
what does Vi stand for?
A
variance attributable to epistatic interactions among alleles at various genetic loci
19
Q
what does Vg =?
A
Vg = Va + Vd + Vi
20
Q
what is narrow sense heritability?
A
the proportion of total phenotypic variation that is due to additive genetic variation
21
Q
what is the equation for narrow sense heritability?
A
h^2 = Va/Vp
22
Q
what is narrow sense heritability used to predict?
A
the response to selection
23
Q
what happens when components of variation act independently?
A
their effects are additive
24
Q
what does high heritability not prevent?
A
environmental changes from having a big effect
25
what does low heritability not prevent?
mutations from having a large effect
26
when does h^2 = 0?
when phenotypic variation is due solely to environmental factors
27
when does h^2 = 1?
when phenotypic variation is due to allelic differences
28
what is directional selection
when smaller or larger traits are favoured (one not both)
29
what is stabilizing selection?
when intermediate values are favoured
30
what id disruptive selection?
when extreme values are favoured
31
what is selection differential?
the difference in trait means before and after selection takes place
32
what is the equation for selection differential?
S = mean(after) - mean (before)
33
what is the selection breeder's equation?
R = h^2 S
34
what does R stand for?
the evolutionary response to selection (change in phenotype between parent and offspring)
35
what does S represent?
the phenotypic variation that influences fitness
36
What can happen if selection is strong?
a population can respond to a trait even if it is only weakly heritable
37
what can happen if a trait's heritability is high?
even weak selection can lead to evolutionary change
38
when does the most rapid evolutionary responses occur?
when both heritability and selection are strong
39
what is the quantitative trait locus (QTL)?
the chromosomal region with effects on the trait
40
are evolution and selection the same?
no
41
what does the magnitude of evolutionary change depend on?
strength of selection
| heritability
42
what can selection occur without evolution?
when h^2 = 0
43
what is the neutral theory?
The majority variation at molecular level has no affect on survival and reproduction. Frequency of most alleles is determined by Genetic Drift
44
what did Motoo Kimura and colleagues describe in 1968 and 1969?
several observations that do notsupport the hypothesis that NS is responsible for most genetic variation within and between species
45
what observations lead to the neutral theory?
1 . Levels of polymorphism at allozyme loci within species are too high to be maintained primarily by natural selection.
2. The rate of protein evolution is too high to be caused by natural selection. Rates of DNA evolution are even higher.
3. Proteins seem to evolve at a constant rate over time.
46
describe Kimura’s neutral theory
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)
47
what are 2 surprising conclusions regarding neutral theory for genetic drift?
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
48
what does μ represent?
mutation rate
49
in every generation how many new alleles are there?
2N μ
50
what is the chance that every allele in a population has to become fixed?
1/(2N)
51
what is the probability of a new mutation occurring, and going to fixation by genetic drift alone?
1/(2N)x[2N μ]= μ
52
what is the average time to fixation of a neutral allele by genetic drift?
4Ne generations
53
how long may Neutral polymorphism persist in a population?
a very long time causing high levels of protein and DNA polymorphism that we actually observe
54
what are majority of protein evolution mutations?
neutral, fixed in population by drift
55
how are Advantageous mutations fixed in populations?
by natural selection - rare
56
what is the probability of a new mutation occurring and going to fixation by GD alone?
1/(2N) x 2N x μ= μ
57
what happens if μ remains fairly constant over time?
the rate of allele substitution per gene per generation will also remain fairly constant
58
what does natural selection do to the frequency of deleterious mutations?
decreases it
59
deleterious mutations have what kind of impact on the observed rate of allele substitution?
little
60
what are the predictions of neutral theory?
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
what is more common in protein coding genes; synonymous or non-synonymous?
synonymous
62
what is Pseudogenes?
highest divergence rate
63
according to neutral theory, what dominates molecular evolution?
drift
64
what is a hermaphrodite?
an organism that has complete or partial reproductive organs and produces gametes normally associated with both male and female sexes
65
what does the production of males lead to?
twofold cost of sex
66
what are the benefits of sex?
- results in more genetic variation (faster evolution)
- can recombine beneficial mutations
- can clear deleterious mutations
67
what is Muller's Ratchet?
The process by which asexual genomes accumulate deleterious mutations
68
what is the Red Queen effect?
Biological arms race: between hosts and parasites
69
what are the costs of sex?
- two fold cost of sex
- Search costs to find a mate
- Reduced relationship with offspring
- Risk of sexually transmitted disease
70
how do Bdelloid rotifers compensate for the lack of sex?
- 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
what type of environment favours sex?
unstable
72
what kind of environment favours asexual reproduction?
stable
73
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
B.Increase genetic variation to cope with a change in the environment the next spring
74
what is sex?
is the combining and mixing of chromosomes during reproduction (=meiosis and recombination)
75
what is parthenogenesis?
a mode of reproduction in which female sex cells undergo meiosis but are not fertilized by sperm
- produce only daughters
76
what is fecundity?
the reproductive capacity of an individual
77
what is anisogamy?
sexual reproduction involving the fusion 2 dissimilar gametes
78
what is sexual selection?
differential reproductive success due to variation in success at getting mates
79
what is the operational sex ratio (OSR)?
the ratio of male to female individuals who are available for reproducing at a given time
80
what are females limited by when it comes to sex?
of eggs
81
what are males limited by when it comes to sex?
of mates
82
what is intrasexual selection?
male-male competition
83
what is intersexual selection?
female choice
84
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.Male
85
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?
intersexual selection
86
what is a Preexisting Sensory Bias in females?
- 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
what are sexy-sons?
- 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
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
B.Sexy-sons
89
what is polyandry?
females mating multiple times
90
what are advantages of polyandry?
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
what is the dilution effect?
safety in numbers that arises through swamping the foraging capacity of local predators
92
what are the costs of group living?
- Increased conspicuousness to predators
- Increased competition for food
- Increased competition for mates
- Decreased certainty of paternity/ maternity
- Increased transmission of disease/ parasites
93
what are the benefits of group living?
- Increased vigilance
- Dilution effect
- Enhanced defence capability
- Cooperative foraging / hunting
- Improved defence of critical resources
94
what is altruism?
The actor incurs a cost and the recipient benefits in terms of surviving offspring
95
what is the Group selection –v1.0 hypothesis?
Traits can evolve that are costly to the individual as long as they benefit the group
96
what are the problems with group selection?
- 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
what is the kin selection hypothesis?
Traits can evolve that are costly to the individual as long as they benefit kin (relatives)
98
what is inclusive fitness?
inclusive fitness = Direct fitness + Indirect fitness
99
what is direct fitness?
personal reproductive success
100
what is indirect fitness?
weighted reproductive success of genetic relative
101
what does indirect fitness depend on?
coefficient of relatedness, r
102
when does an altruistic allele increases in frequency by Hamilton's rule?
Br> C
103
what is the green beard hypothesis?
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
what is the Reciprocal altruism hypothesis?
Traits can evolve that are costly to the individual as long as individuals are likely to be reciprocated
105
what does w stand for?
probability that a selfless behaviour will be reciprocated`
106
what is the formula for when altruistic behaviour will evolve?
wb-c > 0
107
what is game theory?
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
what is evolutionary stable strategy?
a behaviour that, if adopted by a population in a given environment, cannot be invaded by any alternative behaviour
109
what is an organisms life history?
their scheduleof reproduction and survival
110
what are life history traits closely related to?
fitness
111
what are the ideal life history traits for sexual maturity, producing offspring, and lifespan?
at birth, continuously in large numbers, and live forever
112
what does no species have ideal life history traits?
energetic constraints
113
what are the fundamental trade offs?
- Reproduction and survival (growth)
- Current and future reproduction
- Offspring number and size
114
what is natural selection expected to do in terms of life history?
Maximize number of offspring surviving to maturity, which Depends on likelihood of survival to different age classes
115
what are the 2 hypotheses related to evolutionary theory of aging?
1. The mutations accumulation hypothesis
| 2. The antagonistic pleiotropy hypothesis
116
what does RS represent?
reproductive success
117
is natural selection weaker at beginning or end of life?
end of life
118
what may increase RS?
A mutation causing earlier reproduction and earlier death
119
when do tradeoffs arise?
investment in one trait results in lower investment in another trait due to energy constraints
120
what does lower likelihood of survival encourage?
earlier reproduction, larger number and smaller size of progeny
121
what is the Trivers-Willard hypothesis?
Mothers alter sex ratio depending on condition
- Produce females when mother in poor conditions
- Produce males when mother in good condition
122
what is the mother hypothesis?
risk of reproduction at older age selects for reduced fertility
123
what is the grandmother hypothesis?
loss of fertility associated with shift in investment to grandchildren
124
how can family conflict often be explained?
indirect benefits
125
what types of family conflict are there?
parental conflict
parent-offspring conflict
offspring-offspring conflict
126
when should a mother stop feeding the baby?
benefit (to offspring) > cost (to parent)
| benefit/cost > 1
