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Genetics - BI 312 > Chapter 18: Population and Evolutionary Genetics > Flashcards

Chapter 18: Population and Evolutionary Genetics Flashcards

1
Q

Define mendelian population

A

A group of interbreeding, sexually reproducing individuals that have a common set of genes

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2
Q

Define gene pool

A

A common set of genes withing a group

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3
Q

Define genotype frequency

A

the number of individuals with a given genotype divided by the total number of individuals

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4
Q

Define allelic frequencies

A

The gene pool of a population

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5
Q

Define Hardy-Weinberg Law

A

A mathematical model that evaluates the effect of reproduction on the genotypic and allelic frequencies of a population

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6
Q

What are the six factors in population genetics?

A
  1. Mating patterns
  2. Migration
  3. Mutation
  4. Recombination
  5. Natural selection
  6. Random fluctuation
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7
Q

What are the 5 assumptions of Hardy-Weinberg?

A
  1. Mating is random
  2. Population is large
  3. There is no selection
  4. No mutation
  5. No migration
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8
Q

Define genetic drift

A

Changes in allele frequency due to random factors

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9
Q

Does genetic drift affect large populations or small population more?

A

Small

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10
Q

Natural selection has three categories regarding genetics; what are they?

A
  1. Directional selection
  2. Overdominance
  3. Underdominance
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11
Q

Define directional selection

A

One allele has higher fitness than the other

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12
Q

Define overdominance

A

Heterozygotes have higher fitness than either homozygotes

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13
Q

Define under dominance

A

Heterozygotes have lower fitness than either homozygote

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14
Q

What is the difference between relative fitness vs. absolute fitness?

A

Relative: relative to other genotypes
Absolute: measures contribution to next generation

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15
Q

Which type of fitness is most commonly measured?

A

Relative fitness

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16
Q

How do mutations allow scientists to predict evolutionary patterns?

A

Mutation occurs at a consistent rate, changes in DNA can be observed to allow dating of changes and how long ago they occurred

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17
Q

How do you calculate the frequency of an allele?

A

Frequency of an allele = (number of copies of the allele) / (number of copies of all alleles at the locus)

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18
Q

If the requirements of the Hardy-Weinberg law are met, what are the two predictions?

A
  1. The allelic frequencies of a population do not change

AND

  1. The genotypic frequencies stabilize (will not change) after one generation in the proportions p^2 (the frequency of AA), 2pq (the frequency of Aa), and q^2 (the frequency of aa), where p equals the frequency of “A” and q equals the frequency of allele “a”.
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19
Q

Define Hardy-Weinberg equilibrium

A

When genotypes are in the expected proportions of p^2, 2pq, and q^2

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20
Q

(1) Which of the following statements is NOT an assumption of the Hardy-Weinberg law?

a. The allelic frequencies (p and q) are equal
b. The population is randomly mating
c. The population is large
d. Natural selection has no effect

A
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21
Q

(2) In cats, all-white color is dominant over colors other than all-white. In a population of 100 cats, 19 are all-white. Assuming that the population is in Hardy-Weinberg equilibrium, what is the frequency of the all-white allele in this population?

A
22
Q

Define inbreeding

A

A form of non-random mating when organisms have a preferential mating between related individuals.

23
Q

Define inbreeding depression

A

An increase appearance of lethal and deleterious traits caused from inbreeding

24
Q

Nonrandom mating alters the frequencies of _____ but not the frequencies of _____

a. alleles, phenotypes
b. genotypes, alleles
c. phenotypes, genotypes
d. alleles, genotypes

A

b. genotypes, alleles

Nonrandom mating alters the frequencies of genotypes but not the frequencies of alleles

25
Q

Define equilibrium

A

A point at which there is no change in the allelic frequencies of a population

26
Q

Recurrent _____ cause(s) changes in the frequencies of alleles.

a. inbreeding
b. competition
c. mutations
d. cell division

A

c. mutations

Recurrent mutations cause changes in the frequencies of alleles.

27
Q

At equilibrium, how are allelic frequencies determined?

A

By forward and reverse mutation rates.

Ex: If mutation rates are low, the effect of mutation on allelic frequencies per generation is very small

28
Q

Define migration / gene flow

A

An influx of genes from other populations

29
Q

Migration has two major effects. What are they?

A
  1. Causes the gene pools of different populations to become more similar
  2. Adds genetic variation to populations
30
Q

(3) In each generation, 10 random individuals migrate from population A to population B. What will happen to allelic frequency q as a result of migration when q is equal in populations A and B?

a. q in A will decrease
b. q in B will increase
c. q will not change in either A or B
d. q in B will become q^2

A
31
Q

Define sampling error

A

A deviation from an expected ratio due to limited sample size

32
Q

Define effective population size (Ne)

A

When population size is the equivalent number of breeding adults

33
Q

(4) Which of the following statements describes an example of genetic drift?

a. Allele g for fat production increases in a small population because birds with more body fat have higher survivorship in a harsh winter

b. Random mutation increases the frequency of allele A in one population but not in another

c. Allele R reaches a frequency of 1.0 because individuals with genotype rr are sterile

d. Allele m is lost when a virus kills all but a few birds in a population and, just by chance, none of the surviving birds possess allele m

A
34
Q

Define founder effect

A

A way that sampling errors can arise from the establishment of a population by a small number of individuals

35
Q

Define genetic bottleneck

A

A way in which genetic drift arises is when a population undergoes a drastic reduction in size

36
Q

Define fixation

A

When an allele has reached a frequency of 1

Explanation:
Through random change, an allele may eventually reach a frequency of either 1 or 0, at which point all individuals in the population are homozygous for one allele. 0 means an allele becomes lost in a population, and 1 means the allele is “fixed” in the population

37
Q

When an allele reaches a frequency of 0 in a population, it is impossible to get that allele back.

a. True
b. False

A

b. False

The allele can return to the population through migration of another population or by mutation

38
Q

What are the 3 causes of genetic drift?

A
  1. Continuous small population size
  2. Founder effect
  3. Genetic bottleneck
39
Q

Define fitness

A

The relative reproductive success of a genotype

40
Q

Define selection coefficient (s)

A

The relative intensity of selection against a genotype

41
Q

How is natural selection measured?

A

Natural selection is measured as fitness

42
Q

(5) The average numbers of offspring produced by three genotypes are GG = 6, Gg = 3, and gg = 2. What is the fitness of Gg?

a. 3
b. 0.5
c. 0.3
d. 0.27

A
43
Q

Define evolution

A

In the biological sense, refers only to genetic change taking place in a group of organisms

44
Q

Define anagenesis

A

Evolution taking place in a single lineage (a group of organisms connect by ancestry) over time

45
Q

Define cladogenesis

A

The splitting of one lineage into 2 and the two branches no longer have a common gene pool and evolve independently of one another

46
Q

Define species

A

Different kinds or types of living organisms

47
Q

Define the biological species concept.

A

The method used to separate organisms into independently evolving units

48
Q

Define the reproductive isolating mechanism.

A

Any biological factor or mechanism that prevents gene exchange

49
Q

Define prezygotic reproductive isolating mechanisms.

A

The prevention of gametes from two different species fusing together and forming a hybrid zygote

50
Q

Define postzygotic reproductive isolating mechanisms.

A

The gametes of two species may fuse and form a zygote, but there is no gene flow between the two species, either because other resulting hybrids are inviable or sterile or because reproduction breaks down in subsequent generations

Genetics - BI 312 (11 decks)

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