Brainscape's Knowledge GenomeTM

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


See full index

Evolutionary Biology > Lectures 4-6 > Flashcards

Lectures 4-6 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Who came up with the theory of particulate inheritance

A

Gregor Mendel

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

Who believed in the theory of blending inheritance

A

Darwin

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

What was the theory of blending inheritance

A

heritable factors blend to produce an intermediate phenotype

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

Why does the theory of blending inheritance not work

A

because if offspring phenotypes must always be intermediates of parents, all individuals would look the same after just a few generations

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

What are the 3 laws of the particulate theory

A

Law of segregation
Law of independent assortment
Law dominance

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

What is law segregation

A

individuals possess two alleles at each gene – one from each parent

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

What is law of independent assortment:

A

genes for separate traits are passed on independently from parents to offspring (NB this is not always true - remember linkage disequilibrium?)

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

What is law of dominance

A

recessive alleles will always be masked by dominance alleles

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

What are Darwins four postulates after the modern synthesis

A
  1. As a result of mutation, gene flow and recombination, individuals within populations are variable for nearly all traits.
  2. Individuals pass their alleles on to their offspring intact.
  3. More offspring are produced than can survive.
  4. The individuals that survive and reproduce are those with the alleles that best adapt them to their environment.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What were the two schools of thought on genetic variation within populations until 1960

A

Classical and Balanced

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

What did the classical school think

A

Genetic polymorphisms are rare and mainly deleterious. At each locus, the best allele should be fixed by natural selection

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

What did the balanced school think

A

Large amounts of genetic variation are maintained in populations. At each locus, polymorphisms are maintained by “balancing” natural selection

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

Was the classical or balanced school right in there thinking

A

Turned out to be both wrong… but to be fair, they didn’t have any data!)

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

When is it reasonable to use phenotype as a proxy for genotype

A

for discrete variation, where a trait follows a simple Mendelian inheritance pattern e.g

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

When is it not reasonable to use phenotype as a proxy for genotype

A

When you have continuous traits such as height as continous traits are mostly polygenic (controlled by many genes)

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

Ways you can visualise genetic (protein) variation

A

gel electrophoresis

microsatellite genotyping

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

Why was the classical school wrong

A

polymorphisms are not rare

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

Why was the balanced school wrong

A

no evidence that selection maintains all the variation

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

Who argued for neutralism in the selection-neutralism debate

A

Motoo Kimura

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

Who argued for selection in the selection-neutralism debate

A

John Maynard-Smith

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

What is the neutralism stance on the evolution at the molecular level (DNA sequence)`

A

Most variation at molecular level is selectively neutral, fixed by genetic drift
Most non-neutral mutations eliminated by selection
(does not suggest that morphological, physiological and behavioural features evolve by random genetic drift – such features evolve by NS, its just that this make up only a small part of overall molecular variation

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

What is the selectionism stance on the evolution at the molecular level (DNA sequence)`

A

Substantial portion of the genome affected by selection

Selection acts on many genes, and also affects linked sites

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

Reasons why variation is maintained (briefly)

A

various mutational mechanisms/

recombination, natural selection, gene flow recombination

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

What is the observed genotype frequency

A

the proportion of a population that has a certain genotype

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

What is allele frequency

A

proportion of a given allele in the population

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

How to work out the total amount of alleles in sample

A

number in a sample x2

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

What are the assumptions of hardy weinburg equilibrium

A

a. infinitely large population size
b. no mutation
c. no selection
d. no gene flow
e. random mating

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

What can we test with Hardy weinburg equilibrium

A

test whether evolution is occurring and see if one or more assumptions are being violated

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

What is genetic drfit

A

– random fluctuations in allele frequencies occur as a result of ‘sampling error’ between generations in finite populations

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

What can genetic drift lead too

A

Can lead to the replacement of old alleles by new alleles (and the trait they confer) – non-adaptive evolution

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

What are some differences between natural selection and genetic drift

A

GT is non adaptive and can affect all loci/alleles

NS is adaptive evolution and favours mutations that give an adaptive advantage. Does not necessarily affect all alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is a similarity between genetic drift and natural selection

A

Both cause allele substitutions – evolutionary change – in populations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What happens when alleles drift towards fixation

A

the freq of heterozygotes decreases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the bottleneck effect

A

Specific case of genetic drift
occurs when some event causes a drastic reduction in the size of a population. Usually results in loss of genetic variation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the founder effect

A

A colony formed by a small number of founders will suffer loss of genetic variation – rare alleles are likely to be lost

36
Q

What is census size

A

Number of individuals in a population

37
Q

What is Ne

A

effective population size ie

The size of an ideal theoretical population that would lose heterozygosity at the same rate as the actual population’.

38
Q

What 3 factors influence effective population size

A

1) Variation in the number of progeny. If some individuals have more offspring than others, Ne will be reduced
2) Overlapping generations
Individuals mate over multiple generation.
Offspring may mate with parents. They carry identical copies of the same genes, so the effective number of genes in the population is reduced.
3) Unequal numbers of males and females

39
Q

How do fluctuations in population size influence Ne

A

All populations fluctuate in size – the rate of genetic drift is higher in small populations, so Ne is more strongly affected when population is small

40
Q

What is F

A

coefficient of inbreeding

41
Q

What is inbreeding

A

Mating between related individuals

42
Q

When does the inbreeding coefficient increase more rapidly

A

increases more rapidly in small populations than in large populations.

43
Q

Evidence for inbreeding depression on Florida panther

A

Tail kink
Cryptorchidism (>80% males) & deformed sperm
Poor fecundity
High parasite load and disease susceptibility
Atrial septal defects

44
Q

What is inbreeding depression

A

When inbreeding reduces reproduction and survival

45
Q

Consequences of inbreeding

A

Reduces heterozygosity
Exposes rare deleterious recessive alleles (as homozgotes)
Loss of genetic diversity

46
Q

Similarities between inbreeding and genetic drift and what are the consequences

A

Both related to population size

Both have similar effects in terms of reducing genetic diversity

Both increase risk of extinction in small populations
This is why genetic diversity is one of the three global conservation priorities of the IUCN

Both key forces in evolution, especially in small populations

47
Q

Genetic drift influences genetic variability predictably , how is that beneficial

A

if we can measure genetic variation at genes not under natural selection, we can compare patterns of DNA variation from real populations to reconstruct population history

48
Q

Why is is important to know effective poulation size, not just

A

Not all individuals in a census will contribute to the next generation. Thus, genetic drift and loss of heterozygosity will be greater than expected as the population is effectively smaller than it really is.

49
Q

What is genetic rescue due to

A

Gene flow

50
Q

Example of genetic rescue

A

1995 Florida Panther N ≈ 25 with inbreeding depression (last lecture!) … 95% likelihood of extinction in 20 years…

1995 – Eight pumas introduced from Texas (historically linked)

1995-2007 
 Population size stabilises!
 Hz increases!
- Survivorship increases!
- Inbreeding traits decrease!
51
Q

What can cause population structuring

A

Natural aggregations

Fragmented habitats

52
Q

What can population structure lead to

A

It can cause population subdivision and lead to genetic differentiation among subpopulations

53
Q

What can cause genetic differences between populations , and in turn, structural differences

A

Random processes such as genetic drift and mutations

Deterministic processes such as gene flow and selection

54
Q

What is the Wahlund effect

A

Reduction in Hz caused by structure (shown by pooling two populations together)

55
Q

What does a large F mean

A

A larger F means there is greater population subdivision (or inbreeding)

56
Q

How can population structure be quantified

A

quantified using Wrights F (fixation) statistics

57
Q

What is Wrights F (fixation) statistic equation

A

F = (H,exp – H,obs)/H,exp

where Hexp is heterozygosity expected under HWE = (2pq) and Hobs is the heterozygosity observed

58
Q

What will cause a low H,obs

A

Lower Hobs is produced by subdivision into smaller populations -diverging through genetic drift or selection (and/or non-random mating in populations).

59
Q

What are the 3 hierarchical levels of total F (inbreeding coefficient)

A

Individual
Subpopulation
Total population

60
Q

How to calculate Fis

A

Fis = (Hs - Hi)/Hs

61
Q

What is Fis

A

Fis measures - population structure (inbreeding) in individuals relative to subpopulations,

62
Q

What is Fit

A

measures - population structure (or inbreeding) in individuals relative to the total population

63
Q

How to calculate Fit

A

, FIT = (HT - HI)/HT

64
Q

What is Fst

A

measures - population structure (or inbreeding) in subpopulations relative to the total population

65
Q

How to calculate Fst

A

FST = (HT - HS)/HT

66
Q

In terms of F (inbreeding coefficient) , what is Hi

A

Hi this is the OBSERVED heterozygosity of individuals

67
Q

In terms of F (inbreeding coefficient) what is Hs

A

expected Hz in subpopulations – according to HWE

68
Q

In terms of F (inbreeding coefficient) what is ht

A

expected Hz in total population – according to H

69
Q

What happens to genetic structure is there is no migration

A

With no migration, genetic structure will increase over time due to genetic drift

70
Q

What equation shows that genetic structure (Fst) accumulates fastest in small populations

A

FST = 1 – (1 – 1/2N)^t

71
Q

What is gene flow

A

movement of gametes or individuals among populations

72
Q

What are the models of gene flow

A

Isolated population distribution – Island Models
Patchy population distribution – Stepping Stone Models
Continuous population distribution – Isolation-by-distance Model

73
Q

What is the island model of gene flow

A

Discrete populations with individuals migrating from one population to another with equal probability (p)

Model is not realistic in natural populations

74
Q

What is the stepping stone model of gene flow

A

Individuals migrate to neighbouring populations with a defined probability (p) that differs according to factors (e.g. distance)
More realistic
Model is computationally difficult beyond 2 dimensions and most organisms inhabit multidimensional space

75
Q

What is the distance by isolation model

A

Even distribution of continous overlapping populations
Individuals less likely to migrate to more distant sites
Neighbouring populations are genetically similar
Realistic - used in computer simulations

76
Q

How to work out expected change in allele frequency per generation due to gene flow

A 
∆p =  m(p2 - p1)
p1 = allele frequency in recipient population

p2 = allele frequency in donor population

m = proportion of alleles entering a
population through immigration

77
Q

what is migration-drift equilibrium

A

When the level of gene flow matches the level of genetic drift

78
Q

How are gene flow and genetic drift opposing

A

genetic drift leading to the divergence of populations and gene flow homogenising them.

79
Q

What is the isolation by distance model

A

Based on the theory that migration between continuous populations decreases with increasing distance
Direction of migration is random

80
Q

It terms of isolation by distance model, what is a neighbourhood

A

= group of individuals from area 2σ wide

Migration distance is measured as the standard deviation σ (sigma) of the migration distribution

81
Q

What is the relationship between Nb and Nm

A

Nb is analogous to Nm in the island model: an indicator of gene flow

82
Q

What are direct methods of estimating gene flow

A

Mark-and recapture studies
Can be accurate, but don’t take into account what proportion of migrants contribute to gene flow + short term
Tracking marker alleles over a short number of generations
Directly reflects gene flow, but unrealistic in natural populations + short term

83
Q

What are indirect methods of estimating gene flow

A

Statistics derived from allele frequencies

Directly affected by gene flow and long-term, but can be difficult to interpret

84
Q

If you have a high Fst value, what does it mean

A

Highly significant population subdivision

85
Q

What does it mean to have a low Fst value

A

Very little population subdivision

86
Q

How is genetic drift usually measured

A

using F statistics

87
Q

What mechanisms can counter homogenisation by gene flow

A

Selection (& sexual selection) can act to counter the effects of gene flow at the whole genome-level, or at specific genes

Evolutionary Biology (7 decks)

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