breeding concepts

genetics is?

the study of inheritance and variation

inheritance is the transmission of heriditary factors from one generation to another

variation is the difference/deviation from the normal

animal breeding is

the application of knowledge of genetics to the improvement of animals

phenotype

an aboserved category or measured level of perfromance ofr a triat on an indivudal

trait

any obsveraabe or mesurabel characterisitc o fan indicudual

genotype

genetic make up of an individual

envrionental effects

the effect of external foactor son an animls perfronace

genotype by envrionentn

genotypes can differ due to the enviornment

ex: cattle tempermant

intermediate optimum

an intermediate level of performance that is optimum in terms of profitability and function

relative and dependance relationship

relative perfomance of the different genotypes depends upon the EV

Germ plasma decreases on the triangle formation which is

top: elite breeders

middle: mulitplioers

bottom: end users

seedstockers v commerical breeders

seedstockers sells animals to other breeders

commericial breeders sell animls and thier product ofr sonumptions

job of seedstockers

produce animals that best fit the enviornment, management, and economic conditions of the commercial sector

animal improvement doesn’t always mean change

increasing the proportion of animals with optimum performacne

increase uniformity

populaiton measure

anu measure applied to a population and not an individual

importance of variation

source of genetic change

can be used to compare aspects of genetic model

important for selection

populatoin parameters

mean and variance (they both address one trait at a time)

covariation

how 2 traits or values vary together in a population

imporant aspects of covariation

the sign has a practical value

strength of the relationship

amount of change in one variable that can be expected for a given amount of change in another variable

measures of covariation

correlation ( rx,y)

covariance (Cov x,y)

regression (b x,y)

POPULATION MEASURES

covarace give you the _____ of the relationship between the 2 values

SIGN

correlation measures the ? between 2 variables

strength (the cluster around a line)

correlation vlaue scare

closer to +1 = strong positive

closer to -1=strong negative

0= no relationship

regression

the expected or average change in one variable (Y)per unit change in another (X)

the amount of change

regression

population measure

predict a value based on some other piece of information

the slope of the imaginary line

a strong correlation does or deos not necessarily imply a large regression coeeffiecnt

deos NOT

what are true values

an unknown underlying attribute that affects animal performance

PD, PA, Ep, Et, vlaues in prediction

quantatative genetics

predicts the true claue fo ompontetns of the gnetic model using observed phenotype

simply inheritated triats

a trait affected by one a few genes

categorical/qualitative traits

a trait in which phenotypes are expressed in categroies

quantatative traits

a trait in which phenotypes show continuous (numerical) expression

polygenic traits

a trait affected by many genes, no single gene having an overriding influence

ex) coat color, temperment)

are affected by EV

usually described by numbers

simply inherited v plygenic

reder to how thr triat is inherited

epistasis

one gene is modified, masked, or suppressed by one or more other genes

linkage

the occurance of 2 or more loci of interest on the same chromosome

the closer they are more likely they are to be inherited together during meiosis

allele

specific version of a gene

incomplete dominacne

both alleles expressed

roan coat

partial dominance

heterozygous phenotype more closely represents the homozygous dominant phenotype

overdominace

expression of the heterozygous is superior to either of the homozygous

contemporary group effects on exam 100%

animals that are run together without being treated in a certain preference

infulceus all animals in the group equally and may be due to climate or nutrition

why? this minimizes the EV so the difference observes are due to breeding value and genetics

environemtn influences

maternal ability

temporary enviornmental effects

contemporary group and other systemic effects

how can we select and cull to imporve animal perfromance in future generations?

separate EV from genetic/BV and select on an estimate (EBV or EPD)

how can we select and cull to imporve average lifetime performane

selec on an EBV or EPD to change average genetics from generation to generation but for individual we need to provide a beneficial EV

maternal ability calcaltion

= (BV-M) + (EV-M)

hertitability

proportion of variation due to genetic effects

progeny difference

transmitting ability

the difference between the mean performance of the individuals progeny and the mean performance of all progeny

allele combination value

the effect of a combination of alleles of a gene at a particular locus- dominance and epistasis
CANNOT BE TRANSMITTED FROM PARENT TO OFFSPRING

producing abuility

repeated traits for which individuals routinely hae more than one performance record

a function of all factors that permanently affect an individuals perfromance

heritability 100% on exam

measure for the strength of the relationship between performance and breeding values for a trait in a population

when heritability is low an anisml own performance is not likely to be a good indicator of its breeding value