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BIOM2202 > Module 5 > Flashcards

Module 5 Flashcards

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1
Q

What statement describes most accurately an aspect of natural selection

A

Differential reproduction or survivorship are necessary but not sufficient for natural selection to occur

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2
Q

Under Hardy-Weinberg equilibrium

A

Random mating leads to steady allelic frequencies through time

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3
Q

The rate of molecular evolution equals the mutation rate

A

In a neutral model

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4
Q

When there is overdominance genotypes fulfil one of the following fitness scheme

A

AA: 0, Aa: 1; aa: 1-s

–> anything is fine as long as homozygotes are lower than heterozygotes

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5
Q

Non-random mating

A

Is both inbreeding and assortative mating

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6
Q

In very large populations

A

Average heterozygosity remains constant under mutation-drift equilibrium

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7
Q

Populations under mutation-drift balance

A

Carry high levels of heterozygosity when they are large

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8
Q

Selection against deleterious recessive mutations (a)

A

Can be offset by recurrent mutation, leading to mutation-selection equilibrium

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9
Q

Slightly deleterious mutations

A

Reduce fitness slightly

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10
Q

Polymorphism

A

Is related to levels of heterozygosity in the population

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11
Q

If s=0.5 for aa, A is dominant over a, and there are AA:30, Aa:20, aa:50 individuals in the populations, then

A

Aa individuals will increase in frequency in the population

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12
Q

If s=0.2 for aa in Environment 1, and s=0.2 for AA in environment B (all other genotypes in each environment have relative fitness of

A

Directional selection in opposing directions is making the two populations more different

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13
Q

Genetic drift

A

Results from Mendelian segregation, particularly in small populations

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14
Q

Reductions in heterozygosity

A

Can occur with non-random mating

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15
Q

Linkage disequilibrium

A

Is used for association mapping

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16
Q

Variation, heredity and fitness differences

A

Change trait distributions in a population

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17
Q

Balanced polymorphisms arise

A

When heterozygotes are preserved, and homozygotes are eliminated in the population

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18
Q

Darwin’s model

A

When combined with Mendel’s model you create population genetics

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19
Q

Recombination

A

Is only cross over between homologous chromosomes

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20
Q

Linkage disequilibrium and recombination

A

Are inversely related

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21
Q

When considering the segregation of two genes with two alleles each: If recombinant gametes are not produced during meiosis

A

Linkage disequilibrium will be positive

22
Q

Darwin proposed that which of the following was the driving force in evolution in nature?

A

Selection

23
Q

Different colored bands on the shells of land snails would be classified as what type of variation?

A

Phenotypic variation

24
Q

The molecular source of variation that underlies the process of evolution is:

A

Mutation

25
Q

n a sample of 400 men, 48 have X-linked color blindness and all the others have normal color vision. What is the frequency for the X-linked color blindness allele, assuming each man is hemizygous for the allele?

A

0.12

26
Q

In a population, whenever the second most frequent allele of a gene has a frequency greater than 0.01, we refer to the situation as

A

Genetic polymorhism

27
Q

Which of the following is most effective at fixing the recessive allele in a population?

A

Selection for a recessive allele

28
Q

Selection that favors intermediate values of a trait at the expense of extreme values is known as:

A

Stabalising

29
Q

Selection that favors extreme values of a trait at the expense of intermediate values is known as:

A

Disruptive

30
Q

The decay of heterozygosity in a population is proportional to

A

1/2N

31
Q

Selection involving which of the following creates a dynamic equilibrium in which different alleles are retained in a population despite their being harmful in homozygotes

A

Balancing

32
Q

Selection against a deleterious recessive allele that is replenished in the population by mutation leads to a dynamic equilibrium in which the frequency of the recessive allele is a simple function of the mutation rate and the selection coefficient represented by which of the following?

A

q = sqrt(u/s)

33
Q

A population’s acquisition of selectively neutral alleles through mutation is balanced by the loss of these alleles through genetic drift. At equilibrium, the frequency of heterozygotes involving these alleles is a function of the population’s size and the mutation rate is:

A

H = 4Nu/(4Nu+1)

34
Q

Mice with the genotype Hh are twice as fit as either of the homozygotes HH and hh. With random mating, what is the expected frequency of the h allele when the mouse population reaches a dynamic equilibrium because of balancing selection?

A

0.5

35
Q

How does the nearly neutral theory modify the neutral theory of molecular evolution?

A

Fixation of slightly deleterious alleles is possible in small populations and therefore these populations evolve faster

36
Q

A gene has three alleles, A1, A2, and A3, with frequencies 0.6, 0.3, and 0.1, respectively. If mating is random, predict the combined frequency of all the heterozygotes in the population.

A

0.54

37
Q

In a survey of moths collected from a natural population, a researcher found 60 dark specimens and 40 light specimens. The dark moths carry a dominant allele, and the light moths are homozygous for a recessive allele. If the population is in Hardy–Weinberg equilibrium, what is the estimated frequency of the recessive allele in the population? How many of the dark moths in the sample are likely to be homozygous for the dominant allele (round up digits)?

A

13

38
Q

In some regions of west Africa, the frequency of the HBBS allele is 0.1. If this frequency is the result of a dynamic equilibrium due to the superior fitness of HBBSHBBA heterozygotes, and if HBBSHBBS homozygotes are essentially lethal, what is the intensity of selection against the HBBAHBBA homozygotes?

A

0.11

39
Q

If the evolutionary rate of amino acid substitution in a protein is K, what is the average length of time between successive amino acid substitutions in this protein?

A

The reciprocal of the rate, that is 1/K

40
Q

In a coding region of a gene you, where would you most likely find silent polymorphisms?

A

Four-fold degenerate sites

41
Q

Most silent (synonymous) mutations are:

A

Neutral

42
Q

Under neutrality, what will happen to most new neutral mutations in a population initially (= first 20 generations)?

A

Loss

43
Q

Under neutrality, how does the size of the population affect the probability of fixation of a new mutation?

A

It increases the probability of fixation in small populations

44
Q

What is the relationship between the rate of evolution (RE), the rate of substitution
(RS), and the mutation rate (MR) when evolution proceeds by genetic drift?

A

RE=RS=RM

45
Q

When testing the neutral hypothesis of molecular evolution, the dN/dS test will reject it when:

A

dN

46
Q

The McDonald-Kreitman test will provide evidence for neutral evolution when:

A

C) dNp/dSp=dNf/dSf

47
Q

If dN/dS for fixation is greater than dN/dS for polymorphism we could:

A

Reject neutrality

48
Q

The evolution of adaptive traits is better explained by:

A

Selection

49
Q

Functionally important domains of a protein have

A

Lower substitution rates than non-functional domains of a protein

50
Q

Tajima’s D is negative when

A

Populations expand or genes are under selection

BIOM2202 (5 decks)

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