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Veterinary genetics > Genetics and Animal breeding deck 1 > Flashcards

Genetics and Animal breeding deck 1 Flashcards

1
Q

Define a population.

A

a group of individuals of one species that inbreed in the
same place, at the same time, and are isolated from other groups of the same species.

A “basic unit of evolution”.

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2
Q

A term for an association of different organisms forming a closely integrated community.

A

biocoenosis

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3
Q

A species becomes separated into distinct populations due to what key factors that drive evolution?

A

genetic variation between individuals,
natural selection,
isolation.

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4
Q

term for random mating

A

panmixia / panmixis

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5
Q

When is a population referred to as closed?

A

mating with individuals from other populations

does not occur

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6
Q

define gene pool

A

The sum total of all alleles (collective genetic information) carried in all members of a population.

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7
Q

what is population size denoted as?

A

N

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8
Q

what is a sample of a population denoted as?

A

n

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9
Q

another term for random

A

stochastic

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10
Q

The probability of an event is a ratio that is given as?

A

a numerical value between zero and one.

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11
Q

The probability of a sure event is?

A

1

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12
Q

The probability of an impossbile event is?

A

0

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13
Q

What is the multiplication rule?

A

Given the probabilities of two independent events (A and B), the rule states that the probability that both events occur is found by multiplying the probabilities of the events.

p(AB) = p(A) x p(B).

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14
Q

How are different genotype-numbers denoted?

A

D
H
R

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15
Q

How are genotype frequencies denoted?

A

d
h
r

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16
Q

How is d calculated?

A

d = D/N

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17
Q

How is h calculated?

A

h = H/N

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18
Q

How is r calculated?

A

r = R/N

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19
Q

d + h + r = ?

A

always 1

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20
Q

The sum of genotype frequencies always equals?

A

1

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21
Q

Based on what info can absolute counts of alleles in the

population be calculated

A

Based on the numbers of individuals with different genotypes

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22
Q

What does P denote?

A

absolute count of dominant allele

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23
Q

What does Q denote?

A

absolute count of recessive allele

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24
Q

How is absolute count, P calculated?

A

P = 2D + H

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25
Q

How is absolute count, Q calculated?

A

Q = 2R + H

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26
Q

How is frequency of recessive allele denoted?

A

q

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27
Q

How is frequency of dominant allele denoted?

A

p

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28
Q

What is the Hardy-Weinberg principle?

A

the concept that in a panmictic population in genetic equilibrium - gene and genotype frequencies will remain constant from generation to generation.

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29
Q

What is the Hardy-Weinberg formula/equation?

A

p2 + 2pq + q2 = 1

where
p2 is BB
2pq is Bb
q2 is bb

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30
Q

direct mutation is?

A

Change of the allele from normal to mutant

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31
Q

reverse mutation is?

A

change of the mutant allele to normal

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32
Q

The frequency of direct mutations is typically

designated by the letter

A

u

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33
Q

The frequency of reverse mutations is typically

designated by the letter

A

v

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34
Q

Define mutability

A

is the mutation rate of genes.

The mutability of genes varies between different loci.

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35
Q

what is mutation pressure

A

the intensity of the occurrence of mutations

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36
Q

What is mutation pressure dependent on?

A

the ratio between of the direct and reverse mutations in a

population.

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37
Q

Selection coefficient (s) is?

A

a measure of the relative reduction in the contribution a particular genotype makes as compared with another genotype in the population.

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38
Q

If one of the three genotypes (AA, Aa, aa) is completely removed from a generation, this genotype has a selection coefficient of?

A

s = 1

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39
Q

in case of the maximum relative contribution of a genotype to the next generation (none of the animals
possessing a given genotype have been removed), the selection coefficient would be?

A

s = 0

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40
Q

What does W denote

A

the selection value or fitness of all the remaining animals is expressed by W

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41
Q

selection efficiency (Δq) is?

A

The change in gene frequency in the next generation

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42
Q

selection efficiency indicates

A

the rate of improvement in performance (removal of undesirable genes) from selection during a generation.

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43
Q

define random gene drift

A

the change in the frequency of an existing gene variant in a population due to random chance.

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44
Q

define the concept of effective population size

A

The number of individuals that effectively participates in producing the next generation

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45
Q

how is effective population size denoted

A

Ne

46
Q

Genetic relationship between individuals X and Y can be measured by calculating

A

the relationship coefficient (Rxy).

47
Q

the relationship coefficient (Rxy) measures

A

Rxy demonstrates the relative similarity of the genotypes of the two related individuals.

48
Q

The coefficient of inbreeding is denoted?

A

(Fx)

49
Q

define heterosis

A

or ‘hybrid vigor’, or ‘outbreeding enhancement’

is the improved or increased function of any biological quality in hybrid/heterozygous offspring.

50
Q

name two phenomenon that result in change in the proportion of homozygotes and heterozygotes in a population.

A

Heterosis and inbreeding depression

51
Q

explain the dominance hypothesis

A

Heterozygosity will increase in the offspring obtained by crossing homozygous individuals, whereas the offspring can have more dominant genes than either parent.

AA = Aa > aa

52
Q

explain the overdominance hypothesis

A

Overdominance is a condition when the heterozygote is greater in phenotypic value than either homozygote.

AA < Aa > aa

53
Q

What basic parameters do the genetic properties of a population depend on?

A

on gene and genotype frequencies

54
Q

What is The phenotypic value of an individual

A

is the numerical value obtained by measuring a certain phenotypic trait.

55
Q

To analyse the genetic properties of a population, what should be done?

A

the factors affecting the phenotypic values of individuals shall be determined.

56
Q

phenotypic value is denoted?

A

Pi

57
Q

genotypic value is denoted?

A

Gi

58
Q

the phenotypic value/formula can be expressed as:

A

Pi = Gi + E

E being environmental factors

59
Q

Which 3 factors affect the average genotypic value of a population?

A

gene dominance
gene frequency
gene value

60
Q

define breeding value

A

(BV) of an individual is the sum of the mean value of genes or additive genetic value of the individual.

Breeding value is an expression of the genetic potential for increased productivity of an animal.

61
Q

breeding value of an individual is denoted?

A

A

62
Q

How is heritability denoted?

A

h2

63
Q

What is heritability

A

The ratio of the genotypic variance to phenotypic variance

64
Q

how much would low heritability be

A

h2 < 0.3

65
Q

how much would medium heritability be

A

h2 = 0.3 to 0.6

66
Q

how much would high heritability be

A

h2 > 0.6

67
Q

define pleiotropy.

A

occurs when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene.

68
Q

Correlation analysis describes

A

the strength and direction of the relationship between traits.

69
Q

What does BLUP stand for?

A

Best Linear Unbiased Prediction

70
Q

What is the BLUP method?

A

Best Linear Unbiased Prediction is a standard method for estimating random effects of a mixed model.

originally developed in animal breeding for estimation of breeding values and is now widely used in many areas of research.

71
Q

Farm animal selection is aimed at?

A

increasing the frequency of genes that determine the desired traits in a population.

72
Q

The traits appropriate for selection should comply with what 3 criteria:

A

1) trait must be heritable
2) trait must be variable
3) trait must have an economic value.

73
Q

Tandem selection means

A

that selection criteria are changed after one or a few generations.

74
Q

Conventional tandem selection means

A

that selection focuses on one trait until a desired level is reached (several generations), then another trait will be in focus.

75
Q

explain Independent culling levels -method

A

where minimum standards of performance are

established for each trait in the criteria. Those animals who do not qualify with the minimum, are culled.

76
Q

explain selection index -method (SI)

A

where the net values of all traits of the selection criteria are combined into a single index value.

Selection is then based on the ranking of individuals according to index value and those with the greatest values are selected.

77
Q

The single index value is derived utilizing what 3 criteria?

A

the heritabilities of the traits,
correlation among traits,
and economic value of each trait.

78
Q

What is the major criterion for evaluating breeding programmes.

A

Predicted selection response (R)

79
Q

If heritability is 0.3, how much influence do environmental factors have (expressed in %)

A

h2 = 0.3 = 30%

so 70% is up to environment

80
Q

mean Pp

A

average phenotypic value of the selected parents of the next generation

81
Q

mean P

A

average phenotypic value of the initial population

82
Q

mean Po

A

average phenotypic value of the offspring population

83
Q

h2 =

A

R / SD

84
Q

R =

A

h2 x SD

85
Q

“phenotypic variance of a trait in a population” is denoted?

A

sigma squared p

86
Q

define selection intensity and how it it denoted?

A

SD is usually expressed in the units of phenotypic standard deviation of a particular trait. This kind of
a standardized selection differential is referred to as selection intensity (i).

87
Q

phenotypic standard deviation denoted

A

sigma p

88
Q

what is L?

A

generation interval

is the average age of parents when the offspring destined to replace them are born.

89
Q

what is R?

A

selection response

90
Q

what is i?

A

selection intensity

91
Q

what is SD?

A

either selection differential or standard deviation

92
Q

SD is the same as

A

i x sigma p

93
Q

Name 3 types of selection depending on breeding goal

A

stabilizing selection,
disruptive selection,
directional selection

94
Q

describe Stabilizing selection

A

Individuals that display an average phenotypic trait are selected.
Individuals that display extreme traits (+ or -) are culled.

95
Q

describe Disruptive Selection

A

Individuals that display either extreme are selected. Population shifts away from the average trait, towards both extremes.

96
Q

describe Directional Selection

A

This is the most frequently used method in animal breeding.

Individuals that display an “extreme” trait are selected for. Other individuals are selected against.
Population shifts toward this trait (+ or -), away from the opposite. The average phenotypic value for a trait of the offspring differs from that of the parental generation.

97
Q

What is R?

A

denotes selection response - is an expression of the shift in the average phenotypic value of a population within one generation or over a certain period of time.

98
Q

The ratio of the selection response and the selection differential is heritability. whats the formula for this

A

h2 = R / SD

R = h2 x SD

99
Q

reduction of body weight formula and explain components

A

y = a + b multiplied by x

where
y = reduced body weight
a = intercept
b = regression coeff. for weight/age
x = age in days
100
Q

relationship coefficient formula

A

Rxy = 0.5 to the power of n1 + n2 …

101
Q

inbreeding coefficient formula

A

Fx = 0.5 to the power of n1 + n2.. + 1

102
Q

how to calculate p when you do not have known frequencies but you do have absolute numbers

A

p = 2D + H / 2N

103
Q

how to calculate p when you have known genotype frequencies

A

p = d + h / 2

104
Q

how to calculate q when you do not have known frequencies but you do have absolute numbers

A

q = 2R + H / 2N

105
Q

how to calculate q when you have known genotype frequencies

A

q = r + h / 2

106
Q

what is inbreeding

A

Inbreeding is the mating of individuals which are more closely related than are average members of a breed or population.

107
Q

Inbreeding depression is a term used to describe?

A

the unfavorable changes resulting from inbreeding, such as decrease in the performance of inbreds, most noticeably in fertility and hardiness, genetically defective offspring, etc.

108
Q

Active inbreeding is?

A

may occur if animals belonging to a genetically related group are bred to each other, and the probability of recombined genes in the resulting offspring is considered to be lower than expected.

109
Q

Passive inbreeding is?

A

may occur in a small population where a very small number of animals increases the opportunity for loci in the offspring to become homozygous.

110
Q

How does inbreeding affect genotype frequencies in a population?

A

Inbreeding increases the homozygosity of a population.

111
Q

𝝙F represents?

A

the “drift” (change) in inbreeding coefficient. Generally a change that sees increase in homozygosity.

NB! 𝝙F is also used to represent endangered status as a percentage

Veterinary genetics (2 decks)

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