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Biology 1108 > Population Genetics and Hardy-Weinburg > Flashcards

Population Genetics and Hardy-Weinburg Flashcards

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
Environmental factors work on the __________ NOT the __________
phenotype; genotype heterozygotes (Aa) and homozygote dominant (AA) are acted upon equally'
26
Natural Selection
individuals that survive and reproduce will lead to a change in allele frequencies over time
27
What are the four observations natural selection is based on?
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
28
Observation 1) Individuals within a population vary
differences in appearance; color of wolves, blooming time of flowers
29
Observation 2) Some of the variability can be passed to offspring
heritability; offspring tend to have the same or similar characteristics as their parents
30
Observation 3) Organisms produce more offspring than will survive
the capacity to reproduce far outstrips the resources to sustain constantly growing populations
31
Observation 4) Survival and reproduction are not random
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
Natural selection results in...
the survival of individuals who are best for the current environment; if the environment changes they may not be the best adapted anymore
33
Results of Natural Selection
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
Decent with Modification
change in gene frequency in a population over time
35
What do populations do that individuals do not?
evolve
36
Mutations
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
Natural selection only acts on...
variations that already exist
38
What is the source of new genetic variations?
mutations
39
What are the forces of evolution
1) mutation 2) natural selection 3) changes in population size 4) migration 5) non random mating
40
What are the mechanisms that alter frequencies of existing genetic variation?
natural selection; genetic drift (bottleneck effect, founder effect); migration; non random mating
41
Directional Selection
individuals at one extreme of a phenotype range have greater survival/reproductive success
42
Stabilizing Selection
individuals with intermediate phenotypes have greater survival/ reproductive success; decreases genetic variation; very specific
43
Diversifying Selection
two or more different genotypes/ phenotypes are favored; often occurs in a heterozygous environment
44
Balancing Selection
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
What is an example of heterozygous advantage?
sickle cell disease; heterozygotes do not have sickle cell but are carriers which allows them to be immune to malaria
46
Negative Frequency Dependent Selection
a phenotype fitness decreases as its frequency increases (more common the phenotype the less fit the individual is)
47
What is an example of negative frequency dependent selection?
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
Sexual Selection
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
Sexual Dimorphism
differences in males and females; for example male birds are sometimes brightly colored while females are dull and blend in more
50
Genetic Drift
change of allele frequencies due to random loss of alleles from one generation to the next
51
What is the overall effect of genetic drift?
it decreases genetic diversity
52
What affects the rate of genetic drift?
population size, allele frequency, mutation rate, fitness, and migration rate
53
Population Bottlenecks
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
Migration
gene flow occurs when individuals migrate between populations having different allele frequency
55
How does migration affect allele frequencies?
tends to reduce differences in allele frequencies between the 2 populations if migration is high
56
How does migration affect genetic drift?
can accelerate drift if migration leads to formation of a new, isolated populations
57
Founder Effect
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
What are the general affects of bottle neck and founder effect?
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
Positive Assortative Mating
a tendency of like individuals to mate; increases the proportion of homozygotes
60
Negative Assortative (disassortative) Mating
a tendency of unlike individuals to mate; increases heterozygotes
61
Inbreeding
choice of mate based on genetic history; does not favor any particular allele; increases homozygosity in a population
62
Reinforcing Isolation
pre-zygotic and post-zygotic
63
Pre-zygotic
methods that prevent the formation of a zygote (fusion of egg and sperm)
64
Post-zygotic
reduced fitness of offspring; prevents alleles from being passed to subsequent generations
65
What are the five different pre fertilization reproductive barriers?
spatial, gametic, behavioral, mechanical, temporal
66
What is part of the pre-zygotic isolation?
habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation
67
What is part of the post-zygotic isolation?
hybrid inviability, hybrid sterility, hybrid breakdown
68
Hybrid Inviability
sperm and egg fertilize but embryo can not develop past early stages
69
Hybrid Sterility
offspring are born, but the offspring can not reproduce
70
Hybrid Breakdown
hybrid forms they are viable and fertile but future generations from those hybrids have bad genetic abnormalities or are sterile
71
Spatial (ecological) Reproductive Barrier
most important; this is like a physical barrier such as a river
72
Temporal Isolation/Reproductive Barrier
species that breed during different times of day, different seasons, or different years do not mix gametes
73
Behavior Isolation/ Reproductive Barrier
species do not mate because of differences in behavior
74
Mechanical Isolation/ Reproductive Barrier
species do not mate because genitalia do not fit/ physically can not mate
75
Gametic Isolation/ Reproductive Barrier
sperm and gamete can not combine

Biology 1108 (5 decks)

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