Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ENVS 212 > Lecture 7: Genetic Drift > Flashcards

Lecture 7: Genetic Drift Flashcards

1
Q

What is genetic drift?

A

The effects of sampling errors on allele frequencies due to chance events

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are chance events?

A

Events related to survival, reproduction, and inheritance of alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

When are the effects of genetic drift especially important?

A

When HWE assumptions are false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do you need to know to estimate genetic drift?

A

How many individuals in each population are contributing their alleles to succeeding generations

Basically, who breeds and how successful they are

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the “poster child” for genetic drift?

A

Elephant seals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Do elephant seals have high or low genetic variance?

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What two issues have created the lack of genetic variability in elephant seals? What caused these issues?

A

1) Reduction in population size due to overhunting

2) Not much mating because males guard harems, so the effective population size is very low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do allele frequencies change when discussing genetic drift?

A

Random sampling of the genes at the start of the next generation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Drift is truly ___ and ____.

A

random and unbiased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Drift is ___ in smaller populations and ___ in bigger populations

A

stronger, weaker

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

At peak variation, allele frequencies are __:__

A

50:50

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

More drift = __ variation

A

less

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Drift causes populations to differentiate by fixation of alleles without the action of ______

A

natural selection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Genetic drift across many genetic loci causes populations to ____

A

diverge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In the simulation of genetic drift, after 32 generations, did most populations fix for one allele, or was there more of an even distribution of allele frequencies?

A

Populations fixed for one allele

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

If a gene is evolving neutrally…

A

there is no selection acting on it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe a diploid individual

A

two copies of every given gene, one from its mother and one from its father

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a gene tree?

A

A genealogy of genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is coalescence?

A

Tracing the genealogy through time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When the lineages of two gene copies merge, we say that they ___

A

Coalesce

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is mitochondrial eve and what is it an example of?

A

The most recent common ancestor of human mitochondrial DNA. Example of coalescence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Is mitochondrial eve male or female?

A

Female

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How many years ago did mitochondrial eve live?

A

~125,000 years ago

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How was mitochondrial eve discovered?

A

By making a genealogy tracing all human mitochondrial DNA backward in time to the most recent common ancestor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Is the ancestor of all Y chromosomes a male or female?

A

Male

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

True or false: Any two copies of gene share an ancestor at some past time.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Gene trees (do or don’t) always match phylogenetic trees. Why (2 reasons)?

A

Don’t.

Deep coalescence and incomplete lineage sorting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What does Ne stand for?

A

Effective population size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is 2Ne?

A

The amount of generations it takes for two copies of a gene in a diploid organism that is evolving neutrally to get to the common ancestor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is coalescence time?

A

The time to the most recent common ancestor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Does coalescence still apply if selection is acting? If so, what changes?

A

Yes, the time to common ancestor changes

32
Q

What are deep coalescence events?

A

Events where the coalescence of living alleles traces further back in time before the speciation event

33
Q

What is incomplete lineage sorting?

A

Incomplete fixation of gene lineages within species lineages

34
Q

What is effective population size?

A

The number of individuals that would give the idealized population the same strength of drift as an actual population of interest

35
Q

Is Ne always less than or greater than the actual population size?

A

Less than

36
Q

What are 5 reasons why Ne < N?

A

1) Populations fluctuate in size

2) Uneven sex ratio

3) Juveniles and older individuals don’t reproduce

4) Reproductive success is variable among breeding age individuals (some have more offspring than others)

5) Limited dispersal from birthplace

37
Q

Small Ne means _____ drift. Large Ne means ____ drift.

A

strong. weak.

38
Q

Essentially, an infinitely large population would be ___ to genetic drift

A

immune

39
Q

What are two events that cause massive fluctuations in population sizes?

A

Bottleneck, founder effect

40
Q

What is a bottleneck?

A

Population reduced to small size for several generations

41
Q

What is the founder effect? How does genetic drift play a role?

A

When a founder colonizes a new area. Genetic drift accompanies the start of a new founding population

42
Q

Why are alleles under/overrepresented in founding populations?

A

Certain alleles may be missing in the founding population

43
Q

Are small founding populations subject to slow or quick fixation/loss of alleles?

A

Quick

44
Q

Do bottleneck and founder effect events reduce or increase genetic variation?

A

Reduce

45
Q

What is a real-life example of a founder event?

A

Zebra finch

46
Q

What is heterozygosity?

A

The chance that two chromosomes in population have different nucleotides at a given site

47
Q

What is a measure of heterozygosity?

A

Nucleotide diversity (pi)

48
Q

The Sunda founding population of finches was (smaller/larger) and (more/less) diverse than the original population

A

smaller, less

49
Q

What are haplotypes?

A

DNA sequences that differ from homologous DNA sequences at one or more base pair sites

50
Q

What does the plot of heterozygosity vs distance to Ethiopia show us?

A

As colonization occurs, this creates multiple founder events which reduce population size. As a result, there is less genetic variation further from the source

51
Q

Which type of animals commonly experience uneven sex ratios?

A

Domestic animals

52
Q

What are two reasons sex ratios may be uneven?

A

1) sex ratio at birth may be biased

2) females and males survive differently

53
Q

Do fisheries have high or low effective population sizes?

A

Low

54
Q

Does it take more generations for fixation to occur at Ne = 50 or Ne = 5?

A

Ne = 50

55
Q

When p = ___, the time to fixation is greatest.

A

0.50

56
Q

Is selection more effective in large or smaller Ne?

A

Large

57
Q

Does self-fertilization reduce or increase Ne?

A

Reduce

58
Q

Larger organisms tend to have (larger/smaller) Ne.

A

smaller

59
Q

Which bacterium has an Ne much larger than most animals/plants?

A

E. coli

60
Q

is polymorphism spread evenly or unevenly across the genome?

A

Unevenly

61
Q

Where in the genome does polymorphism occur?

A

Introns

62
Q

What is neutral mutation rate?

A

chance per generation that the locus mutates to another allele that does not change an organisms fitness

63
Q

If Ne and μₙ go up, what happens to polymorphism?

A

Polymorphism increases

64
Q

Deleterious alleles are weeded out by …

A

Purifying selection

65
Q

In non-coding regions (introns), heterozygosity and polymorphism is ___

A

higher

66
Q

What are selection sweeps?

A

Strong positive selection on a beneficial allele causes that allele to go to fixation

67
Q

What happens to genetic variants/mutations near the beneficial allele?

A

They increase

68
Q

Why is heterozygosity reduced near the center and ends of a chromosome?

A

Recombination is lower

69
Q

Where are selective sweeps and background selection stronger?

A

Where there is less recombination

70
Q

What is fecundity?

A

Offspring per day

71
Q

What is heterozygosity related to? (3 things)

A

Population size
Fecundity
Propagule size

72
Q

Propagule size and fecundity are ___ related.

A

Inversely

73
Q

For species that have large Ne, is selection or drift more powerful?

A

Selection

74
Q

What is codon bias?

A

Bias towards efficient codons

75
Q

What did inbreeding in a population of Adder snakes result in?

A

Loss of non-deleterious alleles

76
Q

How were the problems with the inbred Adder snake population fixed?

A

Males from different populations were introduced

ENVS 212 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions