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Selection Flashcards

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1
Q

What is the most effective means to influence rate of genetic change?

A

selection

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2
Q

How does selection result in genetic change?

A

alters genetic frequency

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3
Q

How do mating systems result in genetic change?

A

genotypic frequency change

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4
Q

How can animals within a population appear different?

A

within a population there is huge variation in types of alleles and how they combine

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5
Q

What happens to the mean of a population as you select for best traits?

A

shifts the mean

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6
Q

What does rate of genetic selection depend on?

A
  • heritability
  • selection differential
  • population size
  • generation interval
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7
Q

How does heritability affect rate of genetic selection?

A

higher heritability results in faster rate of change

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8
Q

What happens if a trait is lowly heritable?

A

they don’t respond as fast to selection

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9
Q

What is selection differential?

A

the mean value of selected individuals subtracted by the mean value of population from which they were selected

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10
Q

How does population size affect rate if genetic seleciton?

A

a greater population size results in greater superiority

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11
Q

What is generational interval?

A
  • average age of parents when the offspring are born

- average number of years for turnover of a population

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12
Q

Is a longer or shorter generational interval better?

A

shorter

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13
Q

What are the sources of information for basis of selection?

A
  • individual performance
  • pedigree-ancestors
  • collateral relatives
  • progeny
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14
Q

What is the purpose of the basis of selection?

A

to judge which animal is best

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15
Q

What are examples of individual performance?

A

weight, feed efficiency, milk data, etc

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16
Q

What is a problem with individual performance?

A

has limitations

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17
Q

What is pedigree?

A

information based on ancestor performance (tells who is the sire, dam, and cousins of individual)

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18
Q

Where do you get pedigree information?

A

is provided to you

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19
Q

What is collateral relatives?

A

half or full siblings

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20
Q

What does progeny measure?

A

the genetic worth of animal by looking at offspring

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21
Q

Until you can evaluate the offspring…

A

you cannot fully evaluate the animal

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22
Q

What is the best source of information for selection?

A

progeny

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23
Q

What is accuracy of selection a measure of?

A

the relationship between the true breeding values and the predicted breeding values

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24
Q

The more accurately we predict breeding values…

A

the greater the probability that the animals we choose to be parents will be the best parents

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25
Q

What is the most important parameter you can measure?

A

breeding value

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26
Q

What is the formula for accuracy of selection?

A

ACC=square root (H^2)

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27
Q

What does the accuracy of selection depend on?

A
  • heritability
  • number of records
  • adjusting for environmental factors
  • contemporary groups
  • careful measurement
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28
Q

What records are being looked at?

A

progeny and other relatives

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29
Q

Are more or less records better for accuracy?

A

more

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30
Q

How do you adjust for environmental factors?

A

make sure things that can influence performance are accounted for so you only are measuring potential of the animal and not the environment

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31
Q

What do you do with contemporary groups?

A

compare animals born at the same time and kept within the same environment

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32
Q

What does it mean to take careful measurements?

A

take measurements in the same point across the animal

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33
Q

What is the accuracy of selection in simple terms?

A

the relative reliability of estimate

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34
Q

What is the accuracy of selection statistically?

A

estimate of how accurately the genotype of the individual for a certain trait can be predicted from the phenotypic averages of it’s relatives

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35
Q

What does the accuracy of selection not suggest?

A

genetic net worth of an animal

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36
Q

Is accuracy of estimate permanent or will it change over time?

A

will change over time

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37
Q

How is accuracy of selection affected by progeny (in terms of graph)?

A

as you have more progeny, the accuracy increases and eventually plateaus

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38
Q

How is accuracy of selection affected by half sibs (in terms of graph)?

A

not as good as full sibs

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39
Q

How is accuracy of selection affected by full sibs (in terms of graph)?

A

higher accuracy in full sib compared to half because have both same parents

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40
Q

What is selection intensity?

A

a measurement of how “choosy” breeders are in deciding what animals will become parents

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41
Q

What does high selection intensity mean?

A

choose only the very best individuals

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42
Q

Parents selected with high intensity should be _____ than the average.

A

much better

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43
Q

What is the only way to determine the actual genetic worth of an individual?

A

progeny test

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44
Q

In what direction does the mean shift?

A

depends on the trait

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45
Q

How many traits does estimated breeding value measure

A

one

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46
Q

What is the formula for expected breeding value?

A

h^2 ( x - x (line above)) / 2

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47
Q

In EBV, what does x represent?

A

individual performance

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48
Q

In EBV, what does x (with line above) represent?

A

mean contemporary group

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49
Q

What is the formula for selection differential?

A

x - x (line over it)

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50
Q

Why is EBV divided by 2 in the formula?

A

half of genetic potential from animal x

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51
Q

In average herd, animal being bred by ___ is average?

A

X

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52
Q

What is the formula for EPD (expected progeny difference)?

A

EBV + X (with line over it)

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53
Q

Will EPD value change?

A

it should change little as it is affected by the bull’s genetics

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54
Q

How do you measure the progress/year?

A

EBV / GI

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55
Q

Is Generation Interval calculated separately for males and females?

A

yes

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56
Q

What is L?

A

the weighted average of males and females

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57
Q

How is there generation interval within a population?

A

different number of males and females and breed at different ages

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58
Q

What is the time it takes to replace all the parents with offspring?

A

average age of the breeding herd when their selected offspring are born

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59
Q

What is the most commonly used source of selection information?

A

individual performance

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60
Q

What is the value of individual performance highly related to?

A

heritability

61
Q

What are examples of highly heritable traits?

A

growth traits, carcass traits, wool traits

62
Q

What are some growth traits?

A
  • birth weight
  • average daily gains
  • yearling weight
63
Q

What are some carcass traits?

A

intramuscular fat,

64
Q

What are some wool traits?

A

staple length

65
Q

What are disadvantages of individual performance (list)?

A
  • sex-limited traits
  • traits requiring long time
  • carcass traits
  • low heritable traits
66
Q

Why are low heritable traits a disadvantage of individual performance?

A

low accuracy

67
Q

What are types of traits are lowly heritable traits?

A

reproductive/fertility traits

68
Q

What are some reproductive/fertility traits?

A

yearling pregnancy, breeding rate, days open, first service conception, calving ease

69
Q

What is first service conception?

A

getting pregnant at 1st service (at first breeding)

70
Q

What are lowly heritable traits (definition)?

A

environment has more effect that genetic

71
Q

heritability formula?

A

genetic variance / phenotypic variance

72
Q

What affects pedigree?

A
  • degree of relationship
  • heritability of trait
  • environmental correlation between ancestor and individual
  • how well trait was measured
73
Q

What is the degree of relationship to parents?

A

1/2

74
Q

What is the degree of relationship to grandparents?

A

1/4

75
Q

What is the degree of relationship to great-grandparents?

A

1/8

76
Q

How does environmental correlation b/n ancestor and individual affect pedigree?

A

if ancestor was under a better or worse environment it can affect performance

77
Q

What are advantages of pedigree?

A
  • cheap
  • valuable for sex-limited traits
  • valuable for traits expressed later in life
  • low heritable traits
78
Q

How is pedigree cheap?

A

data is cheap and online

79
Q

How is pedigree valuable for sex-limited traits?

A

can see the female on both sides

80
Q

How is pedigree valuable for traits expressed later in life?

A

see how generationally a trait has been performed

81
Q

What are the disadvantages of pedigree?

A
  • lack of accurate records/environmental influences of ancestors performance records
  • provides no comparative basis for selection among individuals that are all descendants of the same ancestor
82
Q

What does full sibs mean?

A

same parents

83
Q

What does half sibs mean?

A

one parent in common

84
Q

What is the value of collateral relatives?

A
  • sex-limited traits
  • traits that require slaughter to measure
  • accuracy tends to be lower than individual performance except for lowly heritable traits
85
Q

Why don’t lowly heritable traits have lower accuracy for collateral relatives than individual performance?

A

because of increased number of observations

86
Q

What affects the accuracy of a sib test?

A
  • heritability of trait
  • relationship of sib (closeness)
  • number of sibs tested
  • correlation between phenotypes of sibs
87
Q

If you use the correlation between phenotypes of sibs, what should you make sure is true?

A
  • environmental correlation is high

- full sibs have maternal environment from conception to weaning

88
Q

How related are full sibs?

A

1/2 related

89
Q

How related are half sibs?

A

1/4 related

90
Q

If you are interested in determining the genetic worth of an animal what do you do?

A

progeny test

91
Q

What is progeny testing?

A

evaluation of the genetic makeup of an individual by phenotype of it’s progeny

92
Q

What are the 2 traits can progeny tests be performed for?

A
  • qualitative traits

- quantitative traits

93
Q

What is the major objective of progeny testing for qualitative traits?

A

help determine the likelihood that an animal is a carrier of detrimental recessive allele

94
Q

What is an example of a disorder caused by detrimental recessive allele?

A

CID or SCID

95
Q

What does CID stand for?

A

combined immunodeficiency

96
Q

How is CID carried genetically?

A

autosomal recessive

97
Q

What does autosomal recessive mean?

A

need 2 recessive alleles to show the trait

98
Q

What does CID cause?

A

decreased immunity due to defect in a gene, susceptible to infection as maternal immunity wanes

99
Q

What animal does CID happen in?

A

Arabian horses

100
Q

Is CID lethal? When do they die?

A

yes; around 2 months

101
Q

How do animals normally fight infection?

A

get immunity built up from colostrum from mother

102
Q

What diseases are horses with CID susceptible to?

A

pneumonia

103
Q

Why do animals with CID die around 2 months?

A

immunoglobulin level decreases to a point where they cannot do anything

104
Q

What gene is defected that results in CID?

A

DNA-PKcs

105
Q

What does DNA-PKcs stand for?

A

DNA protein kinase catalytic subunit

106
Q

What amino acids are phosphylated?

A

tyrosine, threonine, and serine

107
Q

What happens when Tyrosine, Threonine, and Serine are phosphylated?

A

enabled them to perform protein folding

108
Q

What does protein folding allow to happen

A

Can see resumption of immune system in animal

109
Q

What factors affect the “success” of progeny test for qualitative traits?

A
  • genetic make-up of animal (genotypes available)

- number of offspring that can be produced

110
Q

What does the number of offspring required to determine the likelihood an animal isn’t a carrier of a detrimental trait depend on?

A

type of potential crosses

111
Q

What are the types of test matings?

A
  • sire x recessive (H_ x hh)
  • sire x heterozygote (H_ x Hh)
  • sire x daughter (H_ x H_)
112
Q

What are the advantaged of sire x recessive test mating?

A

fewer matings required

113
Q

What are the disadvantages of sire x recessive test mating?

A

finding recessive animals

114
Q

What are the advantages of sire x heterozygote test mating?

A

known carrier

115
Q

What are the disadvantages of sire x heterozygote test mating?

A

ID animals, more matings

116
Q

What are the advantages of sire x daughter test mating?

A

easier to obtain, test for any recessive

117
Q

What are the disadvantages of sire x daughter test mating?

A

inbreeding depression, many progeny required

118
Q

What is the major objective of progeny testing for quantitative traits?

A

determine the breeding value of parents

119
Q

offspring represent ___ BV of parent?

A

1/2

120
Q

What is the basis for EPD’s and EPV’s?

A

offspring are 1/2 BV of parent?

121
Q

What factors affect the accuracy of progeny test for quantitative traits?

A
  • dams must be random
  • offspring tested in same environment
  • compare parents of a similar age, environment
  • increased number of progeny = increased accuracy
122
Q

If for accuracy of progeny test on the tables you get above 1, what is that saying?

A

progeny testing is ___% more accurate than

if got 1.35, then 35% more

123
Q

as heritability increases, more…

A

progeny are required to equal accuracy of individual performance

124
Q

Progeny testing is an excellent tool to predict _____________ when _________.

A

future parental performance; heritability is low to moderate

125
Q

What is the net value of animal dependent on?

A

several traits

126
Q

Are the traits the net value of an animal depends on equal in economic value?

A

maybe, may not be (depends on who is picking the trait cow/calf vs feedlot for example)

127
Q

Are the traits the net value of an animal depends on dependent on one another?

A

maybe, or they may be independent of one another (which would mean as one trait improves, the other might decline)

128
Q

What are the three basic methods of selection for more than one trait?

A
  • tandem
  • independent culling method
  • selection index
129
Q

What is tandem?

A

trying to improve one trait at a time (select for one trait, then select for another, then another…)

130
Q

What are problems with Tandem?

A
  • genetic relationship between traits
  • more traits = slower progress
  • takes a long time

-milk production vs fat %, if you improve for production and then move to fat, you will lose some produciton

131
Q

What is independent culling method?

A

set up minimum standards and the animals must meet this standard before it is selected for breeding purposes. You set up multiple standards, and if an animal fails in just one standards you don’t select it.

132
Q

What is a problem with independent culling method?

A

cull animal outstanding in one trait

133
Q

What requirements must a pig meet in order to be saved for breeding?

A
  • from a litter of 8 weaned
  • must weight 180 lb at 5 months of age
  • no more than 1.3 inches of backfat at 200 lbs live weight
134
Q

What is selection index determined?

A
  • place different degrees of emphasis on traits of interest

- make equation to determine genetic worth of animal, based on your objectives

135
Q

Are traits in selection index’s value determined together or separately?

A

separate determination of the value for each trait selected for and the addition of these values gives a total score

136
Q

What is the formula for selection index?

A

I = b1x1 + b2x2 + …. bnxn

137
Q

In selection index formula, what is I?

A

index value

138
Q

In selection index formula, what is b1?

A

weighing vector

139
Q

In selection index formula what is x1?

A

single item of phenotypic information

140
Q

What is selection index value?

A

a single number that predicts the breeding value of an individual for a weighted combination of traits

141
Q

What does BLUP stand for?

A

Best Linear Unbiased Prediction

142
Q

What is BLUP a modification/extension of?

A

selection index

143
Q

What does BLUP involve?

A

simultaneous solution of number of equations using matrix algebra

144
Q

What is BLUP?

A

a method of genetic prediction (for selection) particularly appropriate when performance date comes from genetically diverse contemporary groups

145
Q

What are the keys for selection based on more than one trait?

A
  • genetic relationship among traits
  • number of traits selected for
  • heritability of traits
146
Q

What are factors of genetic relationship among traits?

A
  • positive or negative relationship

- how strong relationship is

147
Q

Is a positive or negative relationship better for selection of more than one trait?

A

positive (high correlation)

148
Q

Are more or less traits selected for better for selection of more than one trait?

A

less because more = slower progress

Genetics (24 decks)

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