exam 3 Flashcards
1
Q
Rxy =
A
relationship coefficients btwn individual x and y
2
Q
n =
A
number of arrows from individual x to individual y through common ancestor
3
Q
Fa =
A
inbreeding coefficient of common ancestor
4
Q
Fx =
A
inbreeding coefficient of individual x
5
Q
Fy =
A
inbreeding coefficient of individual y
6
Q
what is the relationship coefficient?
A
- the co-efficient (#) for expressing the degree of relationship btwn 2 individuals
- expression of the probability that two individuals possess identical genes
7
Q
what is possible change?
A
- the measure of the potential error associated with EPD values
- expressed as “+” or “-“ lbs of EPD
8
Q
as more info is reported on a specific animal, the accuracy _______ and possible change _______.
A
increases; decreases
9
Q
what does high accuracy mean?
A
- means a higher degree of confidence may be placed in the EPD
- EPD value is not expected to change much as further info is required
10
Q
what does low accuracy mean?
A
means that the EPD may change a great deal as additional information is reported and is not as reliable
11
Q
why do non-parent animals have lower accuracy values?
A
since to progeny information contributes to EPD
12
Q
what are amounts of low accuracy?
A
0.00 - 0.50
13
Q
what are amounts of medium accuracy?
A
0.51 - 0.75
14
Q
what are amounts of high accuracy?
A
0.76 - 1.00
15
Q
when is predicting an individual’s offspring used and not used?
A
- Typical for companion animals (horses), high valued animals (show stock,
seed stock), any animal high on the genetic pyramid - Not used for large commercial herds, because group performance is more
important than individuals
16
Q
what is the definition of heritability?
A
the proportion of phenotypic variation due to additive gene effects
17
Q
what is the definition of breeding value?
A
the genetic transferring ability of a parent to its offspring
18
Q
what are maternal traits?
A
effect that genes of an individual’s dam have on the environment influencing its performance
19
Q
what are direct traits?
A
effect an individual’s own genes have on its performance
20
Q
________ evaluates genetic merit for growth
A
weaning weight EPD
21
Q
________ evaluates genetic merit for mothering ability.
A
milk EPD
22
Q
what is a generation interval?
A
the time it takes to replace a herd with its offspring
23
Q
what is tandem selection for traits?
A
alternating selection among traits across generations
24
Q
what is an independent culling level?
A
a minimum level of performance for each trait
25
what is index selection?
selection based on combined performance
combining performance together into an aggregate number (net merit) - then selection on the combined merit
26
what are the problems of multiple trait selection?
27
what is genetic lag?
the time it takes for any genetic improvement made in the selection program of the top tier of the pyramid to trickle down to commercial level
28
what is genomic inbreeding?
an actual measure of how many and which loci are homozygous through genotyping
29
inbreeding ______s homozygosity and ______s genetic variation
increases; decreases
30
what is genetic load?
the number of unfavorable alleles in an individual/family/population
31
the greater the genetic load =
the greater your chances of having a poor outcome during inbreeding events
32
can you create hybrid vigor in a purebred herd? how?
- by using outbreeding/outcrossing
- creates a small amount
33
what does heterozygosity do in association with heterosis?
heterosis is caused by heterozygosity involving genes with non-additive effects
34
what is the genotypic and phenotypic effect of inbreeding?
it increases homozygosity
35
what does a two-breed rotation stabilize at?
- 2/3 breed A
- 1/3 breed B
36
what does a three-breed rotation stabilize at?
at equilibrium, females are
- 4/7 breed A
- 2/7 breed B
- 1/7 breed C
37
if a trait has a high heritability, what heterosis are we expecting from it?
38
as selection intensity increases, what is the response to selection going to do?
increase
39
what is crossbreeding?
the mating of animals of two or more
different breeds
40
what are the conditions of a 3-breed terminal cross?
- F1 females are created from two purebred lines
- F1 females are then bred to a different breed of sire to produce market offspring
41
what is a three-breed cross?
- crosses consisting of three breeds
- may involve a three-breed rotation cross
- may also logically plow the two-breed cross
42
what is a two-breed cross?
purebred animals of two different breeds are used for crossing and the purity of the parent breeds not changed
43
where does heterosis/hybrid vigor show up in a two-breed cross?
- only the F1 generation shows heterosis
- hybrid vigor is not shown in the parents
44
what is a backcross/crisscross system?
crossbred F1 females are kept for breeding and are mated to non related males from one or the other of the two original pure breeds used in the two-breed cross
45
what does crossbreeding take advantage of?
heterosis since it cannot be fixed within a line or breed
46
what are the practical uses for crossbreeding?
- used by the producer of market animals (non-parent animals)
- used to combine the desirable traits of two or more breeds in their crossbred offspring
47
what is outcrossing?
the mating of unrelated animals within a
breed
48
how do crossbreeding and outcrossing coincide?
although crossbreeding is more extreme than
outcrossing, the genetic effects of both are similar
49
what are the genotypic and phenotypic effects of outcrossing and crossbreeding?
- increases heterozygosity
50
what are the reasons for outbreeding?
- new trait or allele into herd (migration)
- more variation into herd for selection improvement (selection intensity)
- minimize inbreeding
- alleviate “inbreeding depression” in herd
- create hybrid vigor in a purebred herd
51
the _____ different two animals are = the ____ hybrid vigor (more or less)
more; more
52
what is the key difference between outbreeding and crossbreeding?
- outbreeding or outcrossing mates two unrelated (or less related) parents from the same breed
- crossbreeding mates two different breeds
53
______ animals are less likely to breed true than ______ animals.
crossbred; inbred
54
what does heterozygosity mean for crossbred animals?
less likely to transmit the same genes to their offspring
55
what is heterosis (hybrid vigor)?
increased performance (vigor) of the offspring over the average performance of the parents when unrelated individuals are mated
56
how is hybrid vigor being used practically?
- used in recent years or broiler and laying hen production
- utilized on a large scale basis in swine
- in farm-livestock, hybrid vigor has been utilized largely from crossing pure breeds
57
what does hybrid vigor influence?
- hardiness
- greater viability
- faster growth rates
- greater milk production
- greater egg production
58
how do you estimate heterosis in crossbreeding?
by comparing the mean of the F1 offspring with that of the purebred parents
59
what is the genetic explanation of heterosis?
caused by heterozygosity involving genes with non-additive effects
60
what are the three things included in non-additive gene action?
dominance, overdominance, and epistasis
61
what does a decline in vigor due to inbreeding indicate?
- many recessive genes have deleterious effects on the vigor of the animal
- homozygous recessive animals don’t perform as well
62
columbia
produce medium wool and large amounts of meat
63
Dorset
high quality white wool
64
Hampshire
- typically used for meat production
- medium wool
65
Jacob
fine wool
66
Lincoln
fine wool breed
67
merino
fine wool sheep
68
Rambouillet
fine wool sheep
69
Southdown
medium wool sheep
70
suffolk
medium wool and meat production
71
Angora
used for fiber
72
Boer
meat
73
Spanish Goat
meat
74
Nubian
dairy goats
75
when do we typically predict an individual offspring? when do we not?
- typical for companion animals (horses), high valued animals (show stock, seed stock), any animal high on the genetic pyramid
- not used for large commercial herds, because group performance is more important than individuals
76
what are the sources of data for EPDs?
individual, ancestral, collateral relatives, progeny, and genetic data
77
what is the second rule of probability?
the occurrence of one event does not exclude the event of another
78
what is the first rule of probability?
the probability of a single event that is one of a set of mutually exclusive events is the sum of the probabilities of the single events
79
what is MPV?
mean-parent value, or the average of the two parents’ phenotypes
80
what is the equation to find % heterosis?
(F1 - MPV / MPV) * 100
81
what is linebreeding?
a form of inbreeding in which an attempt is made to concentrate the inheritance of one ancestor
82
what is selection for extremes?
selection of animals with high performance in any one trait
83
where are individuals vs groups of animals represented on the population pyramid?
as you move down the pyramid, attention shifts from individual animals to group averages
84
what happens when we focus on two traits for selection?
there is a decrease in response for each trait (compared to single trait selection)
