like alleles

(ex: BB or bb, brown eyes domnant, blue recessive)

unlike alleles

(ex: Bb)

genetic make up

BB vs. Bb vs. bb

the expressed characteristics

P=G+E(P=pheno, G=geno, E=environmental influence)

ex: color, horned vs. polled, birth weight

enviro. can have either larger or small/no influence

ex: summer weather can prevent milk production

primarily determined by genotype

little/no enviro. influence

determined/controlled by a small # of genes

detected by visual observation

ex: hair color, horns

not generally econ. valuable

most traits of econ. importance

show continuous variation

affected by many genes

can be measured

ex: birth weight, milk production, fertility, performance(ADG, efficiency, speed of race horse)

can measure pheno, but can't determine geno

most important tool for genetic improvement

proper selection will change genotype of population slowly over time

prevent some from reproducing and use others to become parents of many offspring

increase freq. of desirable genes, decrease freq. of undesirable genes

% of the phenotype variation that is genetic and transmitted from parents to progeny

(in P=G+E, it is % of P that is G)

the amount by which the average progeny of the animal is expected to exceed the average of the herd/population

best tool for genetic selection

used to compare genetic potential

mating animals of different breeds

want optimal characteristics of each breed

animals of common origin

possess traits that distinguish them from other groups within the species

thru selection/breeding, come to resemble/pass traits uniformly to offspring

increase in productivity of the crossbred progeny that is greater than expected based on the avg. of the parents' performance

ex: avg. weaning weight=500lb, progeny=530lb

-->heterosis adv.=30lb, %heterosis=30/500=6%

↑heterosis, ↓h²

inversely related

 crossbred females used to produce new generation

repro. heterosis=high

heterosis↑ as the # of breeds in cross↑