B & G exam 3

simply inherited trait

Trait affected by 1 or a few loci and minimally affected by environment

Polygenic, quantitative trait

Trait affected by many loci and the environment, but phenotype is often numerical

Polygenic, qualitative trait

Affected by many loci and the environment, but phenotype is placed into categories

easiest to most difficult to improve genetic selection

1 qualitative simply inherited

2 quantitative, polygenic

3 qualitative, polygenic

why is trait selection for a simply inherited trait often easier than selection for a polygenic trait?

only one or few loci affect the trait, environment has minimal effect on a trait

qualitative, simply inherited

coat color

qualitative polygenic

conception rate

quantitative polygenic

calving ease

what trait is polygeneic

conception rate

what is the name given to polygenic traits that are qualitative?

threshold traits

what causes genetic abnomalities to appear in animals

inbreeding

what is genetic abnormality

an undesired phenotype caused by a single locus

genetic abnormalities are___

recessive and segregate in one or a few breeds

coat color in cattle: black or red

red

arthrogryposis multiplex: healthy or diseased

diseased

tibial hemimelia: healthy or diseased

diseased

horns in cattle: horned or polled

horned

porcine stress syndrome: stress resistant or stress susceptible

stress susceptible

Rendement napole: normal or acid meat

normal

hyperkalemic periodic paralysis: healthy or diseased

healthy

OLWS: healthy or diseased

diseased

scrapie: resistant or susceptable

susceptible

spider lamb syndrome: healthy or diseaesd

diseased

double muscling: normal or double muscled

double muscled

developmental duplicaton: healthy or diseased

diseased

bovine brachy spina syndrome: healthy or diseased

diseased

ways to manage/select against a genetic abnormality

crossbreeding

DNA test and cull carriers

DNA test and mate carriers to non carriers

DNA test and only

why can crossbreeding eliminate the appearance of genetic abnormalities?

most genetic abnormalities are recessive and found in only one breed

heritability

ratio of variances

genetic correlations

estimated by the calculation of a correlation

breeding values and progeny differences

estimated by regression

inbreeding coefficients

are estimated by the calculation of a correlation

selection indices

are estimated by regression

what is measured by the mean

average of the observations

what is meaured by the standard deviation

average deviation of an observation from the mean

a larger standard deviation =

observations are more spread out

what is measured by a regression coeeficient

how much one variable is expected to change when another variable changes by one unit

if regression on weaning weight on birth weight is 2lbs…

every 1 lb increase in birth weight, weaning weight increases by 2lbs

__ fall witin one standard deviation of the mean

68%

correlation coefficient mesured what two aspects of covariation

direction, strength

heritability statistic

variance

genetic correlation statistic

correlation

inbreeding coeeficieants

correlation

breeding values and progeny differences

regression

selection indices

regression

what type of distribution is assumed

normal distribution

genotype frequencies change in 5 ways

migration

mutation

selection

random drift

non random mating

allele frequencies change in four ways and not…

non random mating

what is Hardy Weinberg equilibrium

when no forces act on a population

allele frequncies remain contact and genotype frequencies convert to HW proportions

breeding value

sum of additive genetic effects at all loci affecting the trait

gene combination value

sum of dominance and epistatic effects at all loci affecting a trait

progeny difference or transmitting ability

difference between progeny performance of the parent and progeny performance of all parents in a group

what is a repeated trait

a trait that can be measured multiple times on the same animal

examples of repeated traits

milk production, sperm count, litter size, racing speed

permenant enviroment effects

environmental effects that permanently affect trait performance

temporary enviromental effects

environmental effects that temporarily affect trait performance

producing ability

the predicted future performance of a repeated trait in an animal

compare BV and Producing ability

both predict performance

contrast bv and producing ability

breeding value is for selection decisions, producing ability is for culling decisions

Calculating Phenotype

x + BV + GCV + Ep + Et

Calculating Genotypic value

BV + GCV

Calculating Producing Ability

X + BV + GCV + Ep

Calculating progeny difference

½ x BV

Calculating enviromental effects

Ep + Et