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AnSc 313 Genetics > Selection Systems > Flashcards

Selection Systems Flashcards

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1
Q

who is selected

A

individuals
relative - ancestors, siblings and progeny

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2
Q

how are they selected

A

independent culling levels
tandem selection
index of weighted traits

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3
Q

what are correction factors?

A

sex
age of dam
age of calf
singleton vs twin

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4
Q

what is individual selection based on

A

animals own performance
practicle if trait is measurable and expressed early

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5
Q

what is ancestral selection based on

A

weighted average of ancestors
father counts more then grandfather
useful if trait is not expressed early

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6
Q

when do you use ancestral selection

A
  • when individual is not available
  • use at least one relative on both the dam and sire side of the pedigree (same relatives for each individual)
  • use closest relative available
    use mean of relatives if theres many records
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7
Q

what is the genetic selection of a horse

A

long generation
few offspring
late mating
training is a cofounding factos
improvement is slow

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8
Q

what is genetic selection for dogs and cats

A

obedience tests
traiing is also a confounding factor
ancestral selection
progeny or sub selection (littler success, breeders should maintain contact and follow up)

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9
Q

how is selection typically done?

A

need to select for more than one trait
negative traits doesnt mean detrimental and positive doesnt mean bene ficial

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10
Q

how does genetic correlation effect meat quality?

A

marbling score and backfat thickness, lean yeild and shear force
marbling is good the more abundent the better

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11
Q

what are independent culling levels

A

select for minimum value per characteristic, no averaging
useful for multipurpose animal
potentially cull many animals

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12
Q

what is ROP bulls?

A

record of performance
30 cm scrotal circumference
pass on feet and legs
above average weight gain for breed

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13
Q

how do you choose to rebreed a cow in the herd?

A

they must produce a calf
must mother well to that calf
must not be dangerous (have temperament problems

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14
Q

What is tandem selection?

A

seelcting for most important trait this season and second most important trait next season

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15
Q

when is tandem selection efficient ?

A

if all desired traits are positively correlated
BUT- in reality used primarily as a temporary selection to focus on the most important trait

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16
Q

what is index selection?

A

use a formula to simultaneously select for several traits, emphasizing some more than others

17
Q

what is indirect selection?

A

use of a correlated trait to select for another trait

18
Q

When is indirect selection useful?

A

traits that are difficult to measure
traits with low hieratability but high relevancy

19
Q

What does response to selection depend on?

A

generation interval
selection intensity
variation in population
hieratability of trait
accuracy of selection
effective population size

20
Q

what is generation interval?

A

average time in years between when an animal and its replacement are born
affected by: gestation length, age at puberty and like sex replacement

21
Q

what is selection intensity

A

average proportion of animal selected
fewer males kept then females
smaller proportion of litter bearers
based on animals kept - expressed as a standard deviation

22
Q

what is variation selection diferences

A

change in lb, litter size
its a selection group vs the total group

23
Q

what is hieretability?

A

the likelyhood of offspring developing a trait from parentage

24
Q

what is accuracy of selection?

A

ranges from 0-1 and depends on
method of selection and number of measurements

25
Q

what is effective population size

A

must be large enough to avoid inbreeding ans to maintain variation for selection

26
Q

what is genetic gain?

A

genetic improvement over time

27
Q

how do you increase genetic gain

A

increased selection intensity (select fewer but it may decrease genetic variety)
increase accuracy of selection(use individuals instead of pedigree)
increase genetic variation - introduce new quality stock
decrease generation interval - harvesting embryos = very expensive

28
Q

what is compare to contemporaries

A

doesnt really measure improvement
does assess position in industry
see how past animal test and then see how many animals in total have the genetic progress

29
Q

what is improvement over time

A

compare offsprings performance to parents
compare herds performance over many years

30
Q

what is a repeat mating design

A

compare new bull to old bull - breed young females with old bull and old females with young bulls
transport stored emyros and fresh embryos in one season
compare performance of calves

31
Q

what happens if there is no progress

A

you hit a plateau
that is the peak of that progress

now it cant grow without serious fertility problems

32
Q
A

AnSc 313 Genetics (23 decks)

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