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Biology 1114 > Random Events > Flashcards

Random Events Flashcards

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1
Q

What is a gonochoric (dioecious) population?

A

A species with two sexes

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2
Q

Do males or females have higher mating success?

A

Females

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3
Q

When a few founders move to a new area but keep the same genetic variation as the parental population

A

Founder event

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4
Q

Is it likely a founder event will produce homozygosity? Why?

A

It is not likely to produce homozygosity because as you add individuals to the founding population the chance of all being homozygous exponentially shrinks

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5
Q

Random change in allele frequencies between generations

A

Genetic drift

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6
Q

END OF SLIDE 5

A

END OF SLIDE 5

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7
Q

How does sexual reproduction reconstruct low-load genotypes?

A

Through recombination and independent assortment

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8
Q

Does a small or large population experience more genetic drift?

A

Small. Large pops follow more closely to HW

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9
Q

A function of rate of drift and rate of mutation

A

Genetic polymorphism

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10
Q

What reduces heterozygosity and thus reduces genetic variation?

A

Genetic drift

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11
Q

The does the f value tell us?

A

Homozygosity. The chance of drawing two identical alleles

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12
Q

What is the consequence of Mullers ratchet?

A

Over time, the population with low fitness genotypes increases and causes a decrease in the population size as genotypes slide off the end of the scale

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13
Q

START OF SLIDE 3

A

START OF SLIDE 3

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14
Q

How does natural selection act on the highly negative mutations?

A

It gets rid of them right away through purifying selection

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15
Q

What two ways can the founder effect occur?

A
  1. An allele is lost and another becomes more frequent

2. No alleles are lost but one allele is more frequent

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16
Q

What increases heterozygosity and thus increases genetic variation?

A

Mutation

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17
Q

How does migration (gene flow) violate HW?

A

By introducing or removing alleles from the population

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18
Q

END OF SLIDE 2

A

END OF SLIDE 2

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19
Q

What is Mullers ratchet a disadvantage for?

A

Asexually reproducing individuals

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20
Q

What is a tornado or other natural disaster wiping out a large population of plants and effectively getting rid of a particular allele in the process an example of?

A

Genetic drift

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21
Q

What two things are needed for the march to homozygosity to be true?

A
  1. Alleles are selectively neutral

2. Evolution has occurred by a random process

22
Q

What is always the eventual result of genetic drift no matter how large the population is?

A

Fixation. One allele being lost

23
Q

Equation for heterozygosity

A

H = 1 - (p^2 + q^2)

24
Q

How does sexual selection stop Mullers ratchet?

A

It allows for the ability to get rid of the bad mutations

25
Q

What two things are good reasons for sexual reproduction?

A
  1. more variability

2. fewer lethals

26
Q

What aspects of evolution are random? Which are non-random?

A

Random: mutation, genetic drift, migration (gene flow)

Non-random: natural selection

27
Q

What two things are evidence that sexual reproduction is good from an evolutionary standpoint?

A
  1. Ubiquity. It is seen everywhere in most eukaryotes
  2. Longevity of sexual lineages compared to asexual lineages (most asexual organisms recently derived from a sexual ancestor)
28
Q

Is heterozygosity related to HW? If so, how?

A

No

29
Q

What leads to mutation meltdown and ultimately extinction?

A

Combined effect of Mullers ratchet and drift

30
Q

How do mutations lead to Mullers ratchet?

A

Most mutations are neutral or slightly negative and an accumulation of these is bad

31
Q

What is the founder effect an example of?

A

A type of population bottleneck

32
Q

When can high mutation rates be advantageous?

A

In an uncertain environment/world

33
Q

Can one allele be favored over the other in genetic drift?

A

No, it is random

34
Q

When an environmental or other catastrophe decimates a large percentage of the population and when the population rebounds, genetic diversity is only a small subset of what existed before. Ex cheetahs

A

Population bottlenecks

35
Q

What is the equation for homozygosity?

A

f = (p^2 + q^2) or f = 1 - H

36
Q

How does sexual reproduction create more variability?

A

Novel combinations of alleles are created quickly and this is beneficial in changing environments

37
Q

Establishment of a population by a few founders which carry only a small fraction of the total genetic variation of the parental population

A

Founder effect

38
Q

What is an advantage of asexual reproduction over sexual reproduction?

A

All or most members of the pop can reproduce and thus reproductive output is much higher due to more individuals reproducing

39
Q

What does the H value tell us?

A

The chance of drawing two different alleles. This is not the heterozygote frequency, a population with no heterozygotes can have heterozygosity

40
Q

When does the speed of Mullers ratchet increase?

A

With decreasing population size

41
Q

Does fixing occur slower or faster in small populations?

A

Faster

42
Q

How does sexual reproduction create fewer lethals?

A

Sex hides or purges deleterious alleles, or just low fitness alleles, from the general population

43
Q

Deleterious alleles will accumulate in an asexual population over time if mutations from bad back to good or neutral are rare. The number of individuals with 0 low fitness mutations will decrease from generation to generation as mutation load increases

A

Mullers ratchet

44
Q

What do most species with two sexes have their sex ratio at?

A

Right around 50/50

45
Q

How do mutation rates in asexually reproducing organisms and sexually reproducing organisms compare?

A

Sexually reproducing organisms experience mutation far less often

46
Q

How does selection act in relation to drift and mutation?

A

May act before, during, or after in relation to them. It can further reduce genetic variation

47
Q

When a population bottlenecks, what is the only way for rebound of genetic variation to occur?

A

Mutation or potentially movement of individuals from pops with more variation

48
Q

What does migration (gene flow) ultimately cause?

A

Maintenance of genetic diversity in the face of natural selection or genetic drift

49
Q

What is the march to homozygosity?

A

Theoretical idea that if drift is the only thing acting on a population, all of the alleles in the population will eventually be the same. The population drifts to homozygosity

50
Q

Standard measure of genetic variation per locus of a population

A

Heterozygosity

51
Q

Do males or females determine the reproductive output of a species?

A

Female

52
Q

What are some examples of the founder effect?

A

porphyria variegata, Huntington’s disease, and polydactyl

Biology 1114 (10 decks)

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