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Genetics (BIOL 4003) > Exam 3 pt 3 > Flashcards

Exam 3 pt 3 Flashcards

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1
Q

balancing selection

A

not evolving toward allele fixation or elimination (more of a flat bell curve)

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1
Q

balacing selection

A

not evolving toward allele fixation or elimination (more of a flat bell curve)

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2
Q

balancing selection occurs because of a

A
  • heterozygote advantage
  • negative frequency dependent selection
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3
Q

selection coefficient

A

looks at the degree to which a genotype is selected against
s = 1 - w

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4
Q

heterozygote advantage will reach equilibrium when

A

sAAp = saap

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5
Q

negative frequency dependent selection

A

rare individuals have a higher fitness than more common individuals
* selection always favors less numerous genotypes
* drives towards balance

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6
Q

disruptive selection

A

favors survival of two or more different genetypes with different phenotypes

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7
Q

disruptive selection typically acts on

A

traits determined by multiple genes

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8
Q

disruptive selection is likely to occur

A

in populations with diverse/different enviroments

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9
Q

stabalizing selction

A

extreme phenotypes are selected against

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10
Q

stabalizing selection tends to

A

decrease genetic diversity
* elimination of alleles that cause variation in phenotypes

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11
Q

genetic drift

A

random changes in allele frequencies due to random fluctuations

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12
Q

genetic drift

A

random changes in allele frequencies due to random fluctuations

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13
Q

over the long run, genetic drift

A

favors either the loss or the fixation of an allele

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14
Q

_ populations have more chance of fixation due to genetic drift

A

smaller

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15
Q

expected number of new mutations

A

= 2N mu

N - number of indi
mu - mutation rate

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16
Q

a new mutation is more likely to occur in a

A

large population

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17
Q

the probability of fixation is

A

the same as the initial allel frequency in the population

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18
Q

when N is large

A
  • higher chance of new mutations
  • higher chance of mutations being eliminated
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19
Q

when N is large

A
  • higher chance of new mutations
  • higher chance of mutations being eliminated
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20
Q

when N is small

A
  • lower chance of new mutation
  • new mutatiosn have a larger chance of being fixed
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21
Q

average number of generations to achieve fixation

A

t = 4N

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22
Q

alelle fixation takes longer in

A

large populations

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23
Q

bottle neck effect

A

population randomly eliminates genotypes, no selection, diversity goes down

could be due to a natural disaster

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24
Q

founder effect

A

a small group of individuals seperates frrom a larger group and starts its own popiulation that all originate from that small group

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25
Q

consequences of founder effect

A
  • founding population has less genetic variation than original population
  • allelic frequencies of founder population differ from the original population
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26
Q

gene flow

A

the transfer of alleles from donor population to recipient population

27
Q

consequences of bidirectional migration

A
  1. reduces allel frequencies differences between populations
  2. enhances genetic diversity within a population
28
Q

assortive mating

A

individuals do not mate randomly
* positive: mate bc of similar phenotypes
* negative: mate bc of dissimilar phenotypes

29
Q

inbreeding coefficient

A

probability that teo alleles for a given gene in an individual will be identical because of a common ancestor

30
Q

inbreeding coeficient

A

sum of (0.5)n(1 + Fa)

n = number of indiv in inbreed path
Fa = breeding coef of common ancesto

30
Q

inbreeding coeficient

A

sum of (0.5)n(1 + Fa)

n = number of indiv in inbreed path
Fa = breeding coef of common ancesto

31
Q

fixation (inbreeding) coefficient

A

probability that an allele will be fixed in the homozygouse condition

32
Q

the value of the fixation (inbreeding) coeff increases as

A

population size decreases

33
Q

frequency of genotypes in inbreeding

A

AA = p2 + fpq
Aa = 2pq(1-f)
aa = q2 + fpq

34
Q

inbreeding effects on gentype frequencies

A

hetrozygote goes down while homozygotes go up

35
Q

inbreeding depression

A

in natural populations, inbreeding lowers overall fitness

36
Q

For a quantitative trait that is polygenic, which of the following would tend to promote a continuum of phenotypes?
* Increasing the number of genes that affect the trait
* Decreasing the effects of environmental variation
* Increasing the mutation rate

A

Increasing the number of genes that affect the trait

37
Q

variance is

A
  • a measure of the variation around the mean
  • computed as a squared deviation
38
Q

a QTL is

A

a site on a chromosome where one or more genes affected quantitative traits are located

39
Q

a genotype–environment interaction.

A

two more more genotypes noto affected the same way

40
Q

In a population of humans, the correlation between height for fathers and their adult sons is 0.24. What is the narrow sense heritability for weight in this population?

Note: hN2 = robs/rexp

A

0.48

41
Q

The mean weight of cows in a population is 520 kg. Animals with a mean weight of 540 kg are used as parents and produce offspring that have a mean weight of 535 kg. What is the narrow-sense heritability (hN2) for body weight in this population of cows?

Note: hN2 = (Xo − X)/(Xp − X)

Where

   X is the mean weight of the starting population

   Xo is the mean weight of the offspring

   Xp  is the mean weight of the selected parents
A

0.75

42
Q

genotype enviroment association

A

certain genotypes found in a particular enviroment

43
Q

quantitative genetics

A

study of traits that can be described numerically and varies measurably

44
Q

frequency distribution

A

Quantitative traits do not naturally fall into a small number of
discrete categories
An alternative way to describe them is a frequency
distribution
* To construct a frequency distribution, the trait is divided
arbitrarily into a number of discrete phenotypic categories

45
Q

Be able to do the following types of calculations: mean, variance, standard deviation, covariance, and correlation (see Section 28.2, Figure 28.2).

A

ope

46
Q

polygenic inheritance

A

transmission of traits that are governed by two or more genes

47
Q

if r > 0

A

as one factor increases, the other factors will increase with it

48
Q

r = 0

A

the two factors are not related

49
Q

r < 0

A

as one factor increases, the other will decreases

50
Q

An r value that is statistically significant need not imply a

A

cause-and-effect relationship

51
Q

quantitative trait locus

A

The location on a chromosome that harbors one or more
genes that affect the outcome of a quantitative trait

52
Q

If VG is very high and VE is very low

A

Genetics is more important in promoting phenotypic variation

53
Q

If VG is very low and VE is very high

A

The environment causes much of the phenotypic variation

54
Q

phenotypic variance

A

sum of genotic variance and enviromental variance

55
Q

genotype-environment association

A

When certain genotypes are preferentially found in a
particular environment

56
Q

heritability

A

the amount of phenotypic variation within a
group of individuals that is due to genetic variation

57
Q

If all the phenotypic variation in a group was due to genetic
variation
* Heritability

A

would have a value of 1

58
Q

heribility value of 0

A

If all the phenotypic variation was due to environmental factors

59
Q

narrow sense heritability

A

The heritability of a trait due to the additive effects of alleles

= r obs / r exp

60
Q

selective breeding

A

the modification of phenotypes in plant and animal species of economic importance by human intervention

61
Q

selective breeding leads to

A

ppopulation becoming monomorphic

62
Q

selection limit

A

when the population starts becoming monomorphic, more selective breeding have no effect

63
Q

realized heritability

A

estimating narrow sense heritability

Xo - X / Xp - X

64
Q

realized heritability

A

estimating narrow sense heritability

Xo - X / Xp - X

65
Q

heterosis

A

when inbred strains are crossed to each other and the offspring are more vigorous than either parent

Genetics (BIOL 4003) (7 decks)

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