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Biology 1108 > Population Genetics and Hardy-Weinburg > Flashcards

Population Genetics and Hardy-Weinburg Flashcards

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1
Q

Population

A

a group of individuals of the same species occupying the same space/ environment that can interbreed

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2
Q

Allele

A

variant of a gene

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3
Q

Genotype

A

genetic makeup; 2 alleles per individual; DD Dd dd

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4
Q

Phenotype

A

physical expression- determined by genotype

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5
Q

Hypothesis

A

proposed explanation for an observation; testable, falsifiable, specific; not an educated guess

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6
Q

Null Hypothesis

A

usually a hypothesis of “no difference”

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7
Q

Alternative Hypothesis

A

(H1) is the opposite of the null hypothesis

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8
Q

What is the hypothesis and null hypothesis of Hardy-Weingburg?

A

hypothesis- populations do not change over time
null- populations do change over time

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9
Q

What does hardy-Weinberg predict?

A

allele and genotype frequencies stay the same generation after generation
equilibrium= no mechanisms that can change allele or genotype frequency

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10
Q

What are the five assumptions of HWE?

A

1) NO mutations or errors during DNA replication
2) NO survival or reproductive advantage for any genotype or phenotype
3) Infinitely large population (no loss of alleles by random chance alone; no genetic drift)
4) NO migration between populations
5) Random mating (no sexual selection of mates; and everyone has the same number of offspring)

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11
Q

What are the two HWE equations?

A

p+q=1
p^2 + 2pq +q^2 = 1

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12
Q

Genotype or phenotype refers to…

A

individuals NOT alleles

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13
Q

Genotype Frequency

A

of individuals of a particular genotype/ size of population

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14
Q

Allele Frequency

A

Total # copies for a specific allele/ total # of alleles

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15
Q

How to find allele frequency of a population?

A

2 times the population

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16
Q

What is p?

A

allele frequency of the dominant allele

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17
Q

What is q?

A

allele frequency of the recessive allele

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18
Q

What is p^2?

A

frequency of homozygous dominant individuals

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19
Q

What is q^2?

A

frequency of homozygous recessive individuals

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20
Q

What is 2pq?

A

frequency of heterozygous individuals

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21
Q

Artificial Selection

A

humans choose characteristics that are desired; selection by promoting the reproduction of organisms with traits perceived as desirable; does not depend on environmental conditions; can result in poorly adapted individuals (may not survive under normal conditions)

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22
Q

What is an example of artificial selection?

A

dog breeding; selecting a trait such as shorter legs and each generation breeding dogs that only has shorter legs until you get the desired breed

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23
Q

Fitness

A

ability to survive and reproduce in a particular environment; if you survive and do not reproduce then fitness lowers and vice versa

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24
Q

Are dominant alleles the most frequent?

A

in some cases recessive alleles shows the most frequency in a gene pool

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25
Q

Environmental factors work on the __________ NOT the __________

A

phenotype; genotype

heterozygotes (Aa) and homozygote dominant (AA) are acted upon equally’

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26
Q

Natural Selection

A

individuals that survive and reproduce will lead to a change in allele frequencies over time

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27
Q

What are the four observations natural selection is based on?

A

individuals within populations may vary; some of the variability can be passed to offspring (heritability); organisms produce more offspring than will survive; survival and reproduction are not random

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28
Q

Observation 1) Individuals within a population vary

A

differences in appearance; color of wolves, blooming time of flowers

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29
Q

Observation 2) Some of the variability can be passed to offspring

A

heritability; offspring tend to have the same or similar characteristics as their parents

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30
Q

Observation 3) Organisms produce more offspring than will survive

A

the capacity to reproduce far outstrips the resources to sustain constantly growing populations

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31
Q

Observation 4) Survival and reproduction are not random

A

limited resources (food, space, water) lead to competition; camouflage increases survival; individuals with characteristics that are better adapted for a particular environment will have a higher fitness

32
Q

Natural selection results in…

A

the survival of individuals who are best for the current environment; if the environment changes they may not be the best adapted anymore

33
Q

Results of Natural Selection

A

favorable inherited variations tend to increase in frequency; unfavorable variations tend to decrease; end result is a change in the traits of a population over generations

34
Q

Decent with Modification

A

change in gene frequency in a population over time

35
Q

What do populations do that individuals do not?

A

evolve

36
Q

Mutations

A

a change in a nucleotide sequence of DNA; primary cause of genetic variation and mutant (recessive) alleles; due to minors errors during DNA replication

37
Q

Natural selection only acts on…

A

variations that already exist

38
Q

What is the source of new genetic variations?

A

mutations

39
Q

What are the forces of evolution

A

1) mutation
2) natural selection
3) changes in population size
4) migration
5) non random mating

40
Q

What are the mechanisms that alter frequencies of existing genetic variation?

A

natural selection; genetic drift (bottleneck effect, founder effect); migration; non random mating

41
Q

Directional Selection

A

individuals at one extreme of a phenotype range have greater survival/reproductive success

42
Q

Stabilizing Selection

A

individuals with intermediate phenotypes have greater survival/ reproductive success; decreases genetic variation; very specific

43
Q

Diversifying Selection

A

two or more different genotypes/ phenotypes are favored; often occurs in a heterozygous environment

44
Q

Balancing Selection

A

creates a balanced polymorphism; two or more alleles are kept in balance and maintained in a population; heterozygous advantage and negative frequency-dependent selection

45
Q

What is an example of heterozygous advantage?

A

sickle cell disease; heterozygotes do not have sickle cell but are carriers which allows them to be immune to malaria

46
Q

Negative Frequency Dependent Selection

A

a phenotype fitness decreases as its frequency increases (more common the phenotype the less fit the individual is)

47
Q

What is an example of negative frequency dependent selection?

A

prey; some predators form a “search image” for prey usually based on prey more commonly in the area; a prey with a rare phenotype (and genotype) is less likely to be recognized (and therefore eaten)

48
Q

Sexual Selection

A

form of natural selection; directly promotes reproductive success; directed at traits that make it more likely to find or choose a mate; in many species it effects male characteristics more than female; can lead to sexual dimorphism

49
Q

Sexual Dimorphism

A

differences in males and females; for example male birds are sometimes brightly colored while females are dull and blend in more

50
Q

Genetic Drift

A

change of allele frequencies due to random loss of alleles from one generation to the next

51
Q

What is the overall effect of genetic drift?

A

it decreases genetic diversity

52
Q

What affects the rate of genetic drift?

A

population size, allele frequency, mutation rate, fitness, and migration rate

53
Q

Population Bottlenecks

A

in general leads to accelerated of genetic drift, reduction of allelic frequency, probability that an allele is lost/fixed is equal to the probability of the alleles initial frequency, greater the frequency the greater the probability it will be fixed in the population

54
Q

Migration

A

gene flow occurs when individuals migrate between populations having different allele frequency

55
Q

How does migration affect allele frequencies?

A

tends to reduce differences in allele frequencies between the 2 populations if migration is high

56
Q

How does migration affect genetic drift?

A

can accelerate drift if migration leads to formation of a new, isolated populations

57
Q

Founder Effect

A

few individuals are founders of a new population in a new area; severe reduction in size of population in founder population; slight reduction is “source” populatioin

58
Q

What are the general affects of bottle neck and founder effect?

A

generally leads to accelerated genetic drift (rate depends on population size); reduction of allelic diversity ( rare alleles are usually lost); reduction in heterozygosity (due to shifting allelic frequencies)

59
Q

Positive Assortative Mating

A

a tendency of like individuals to mate; increases the proportion of homozygotes

60
Q

Negative Assortative (disassortative) Mating

A

a tendency of unlike individuals to mate; increases heterozygotes

61
Q

Inbreeding

A

choice of mate based on genetic history; does not favor any particular allele; increases homozygosity in a population

62
Q

Reinforcing Isolation

A

pre-zygotic and post-zygotic

63
Q

Pre-zygotic

A

methods that prevent the formation of a zygote (fusion of egg and sperm)

64
Q

Post-zygotic

A

reduced fitness of offspring; prevents alleles from being passed to subsequent generations

65
Q

What are the five different pre fertilization reproductive barriers?

A

spatial, gametic, behavioral, mechanical, temporal

66
Q

What is part of the pre-zygotic isolation?

A

habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

67
Q

What is part of the post-zygotic isolation?

A

hybrid inviability, hybrid sterility, hybrid breakdown

68
Q

Hybrid Inviability

A

sperm and egg fertilize but embryo can not develop past early stages

69
Q

Hybrid Sterility

A

offspring are born, but the offspring can not reproduce

70
Q

Hybrid Breakdown

A

hybrid forms they are viable and fertile but future generations from those hybrids have bad genetic abnormalities or are sterile

71
Q

Spatial (ecological) Reproductive Barrier

A

most important; this is like a physical barrier such as a river

72
Q

Temporal Isolation/Reproductive Barrier

A

species that breed during different times of day, different seasons, or different years do not mix gametes

73
Q

Behavior Isolation/ Reproductive Barrier

A

species do not mate because of differences in behavior

74
Q

Mechanical Isolation/ Reproductive Barrier

A

species do not mate because genitalia do not fit/ physically can not mate

75
Q

Gametic Isolation/ Reproductive Barrier

A

sperm and gamete can not combine

Biology 1108 (5 decks)

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