exam 3 Flashcards
define selection
most efficient mean to influence the rate of genetic change and improvement
what helps change the genotype
h^2, selection differential, population size, generation interval
what does h^2 do
the higher it is, the faster the rate of change
what is the equation for selection differential
mean of selected individual - the mean of the population
what is population size
greater size means greater superiority
what is the generation interval
the number of years for a population to turn over
define sources of information
selecting animals to change a population
what four things are sources of information
individual performance, pedigree, collateral relatives, progeny
individual performance is ____________
measurable
define pedigree
the performance of an individual’s ancestors
define collateral relatives
performance of half sibs and full sibs to look at sex-limited traits
define progeny
the best way to measure genetic worth
define accuracy
an estimate of how accurately the genotype of an individual for a certain trait can be predicted from phenotypic average of its relatives
define individual performance
a value highly related to h^2
what are the disadvantages of individual performance
sex-limited traits
traits requiring time
carcass traits
how h^2 traits
define estimated breeding value
a single trait
what is the equation for EBV
h^2(x-mean of x)/2
improvement is ____________
static
define accuracy of individual performance
based on one record
accuracy =
the sqrt of h^2
define pedigree
based on ancestor performance or the degree of a relationship
environmental correlation is between…
ancestors and individuals
what are the advantages of pedigrees
cheap
valuable for sex-limited traits
valuable for traits expressed later in life
low h^2 traits
how are traits measured accurately
by being measured in the same environment at the same age.
what are the disadvantages of a pedigree
inaccurate/no records
no comparative base for selection
can’t see if ancestry is good for a trait
mistakes can happen
what make up collateral damage? describe them
full siblings- same parents
half siblings- one common parent
what are the values of collateral damage
sex-limited traits
traits that require slaughter to measure
accuracy is lower
what factors affect the accuracy of sibling tests
h^2 of a trait
relationship of sibs
number of sibs tested
what makes up the correlation of the phenotype
environmental correlation
maternal environment
full sibs are _______ related
half sibs are ________ related
half
1/4
what are sibs helpful for
showing the accuracy of how h^2
define progeny testing
evaluation of the genetic makeup of an individual by phenotype of its progeny
what does progeny testing look at
qualitative and quantitative traits
what does progeny testing do
help determine the likelihood that an individual is a carrier of a detrimental allele
what factors affect the success of progeny
genetic makeup
number of offspring produced
define test mating
the number of offspring required to determine the likelihood an animal is not a carrier
what is the advantage and disadvantage of sirexrecessive
A- fewer matings required
D- finding recessive animals
what is the advantage and disadvantage of sire x heterozygote
A- known carrier
D- ID animals and more mating
what is the advantage and disadvantage of sire x daughter
A- easy to obtain
D- inbreeding depression, many progeny required
what is the BV of offspring compared to its parents
1/2
what does increased progeny mean
there is an increased accuracy
what does it mean if accuracy equals 1.22
it is 22% more accurate than normal
as h^2 increases…
more progeny are required to equal the accuracy of individual performance
what does net value depend on
several traits
what are the three basic methods of selection
tandem
independent culling method
selection index
define tandem
individually selecting one trait, then another
what are problems with tandem
genetic relationship of traits
more traits means slower progress
long time
define independent culling method
if an animal has below the minimum level in any trait is culled
what’s a problem with independent culling method
the animal may be outstanding in one trait, but below average in another trait, thus getting culled
define selection index
it places different degrees of emphasis on traits of interest
what does selection index determine?
the genetic worth of an animal
what does selection index do
gives an animal a total score by adding all the values
I=
b1x1 + b2x2 + bnxn
what does I, b, and x stand for in the equation
index value
weight vector
single item of phenotypic information
define BLUP
best linear of selection index
extension of selection index
where does performance data come from with BLUP
contemporary groups
what are contemporary groups
age
herd
etc
what are the three keys for selection? describe them
- genetic relationship among traits
how strong a relationship is - number of traits being selected for
more traits means slower process - h2 of traits
correlated response (strength of movement of traits)
what is the most important trait in dairy cows
milk production
what are common dairy breeds
holstein, jersey, gurnsey, brown Swiss, Ayrshire, shorthorn
what traits are selected for in dairy cattle
milk production
fertility
% fat
temperament
calving ease
define total fat
increases with volume
define % fat
increases by unit
what are linear traits in dairy
stature
strength
body depth
dairy form
rump angle
foot angle
what is the h2 of milk production
0.35
what is the fat yield in cows
+0.75
what is % fat in cattle
-0.4
true or false: crossbreeding is constantly used in dairy cattle
false
which breed is best for the pound of milk produced
holstein
what cow has the best % fat
Jersey
what are the two sources of genetic improvement in dairy? describe them
sire- most genetic progress because they produce more
dam- little genetic process
what is dairy selection
the number of progeny vs. dam
what does AI allow for
large progeny
what is selection based on
closeness of females relatives and progeny testing of offspring
what does the DHIA do
create a system of records
what do DHIA records include
performance records of many sources of variation in performance and private cooperative operated through NCSU
what percentage of diary producers participate in DHIA
45%
what are sires selected on
PTA
what are the three keys in DHIA selection
- record systems are based on comparisons of contemporaries on a similar basis
help select the best animal - limited number of traits are selected for
- adoption of technology