Genetic Model for Quantitative Traits Flashcards
what are simply inherited traits?
affected by one or few genes, phenotypes placed into categories
give 3 examples of simply inherited traits
coat color, presence of horns, certain genetic defects
how do environmental factors affect simply inherited traits?
very little
what are polygenic traits?
affected by many genes (no gene having an overriding effect), generally described in numbers, typically quantitative or continuous in their expression
what is an exception to polygenic traits?
dystocia; it is effected by many genes, but is placed into categories like simply inherited traits, from 1-3 with 3 requiring the most assistance
are polygenic traits effected by the environment?
yes, very
what is the most basic model for quantitative traits?
P = mew + G + E
what is genotypic value?
the overall effect of all the genes carried by the animal (singly and in combination) on the phenotype of the animal for the trait, not directly measurable
what two values is genotypic value (G) the sume of?
breeding value (BV) and gene combination value (GCV)
what is breeding value also called?
additive genetic value
what is breeding value?
the part of the genotype that can be transmitted from parents to offspring, the sum of the effects of individual genes independent of the effects of dominance and epistasis, considered as a parental value
what must be done before selecting animals to be parents?
their breeding values must be estimated and the best BV must be chosen to get the best result
how much of their genes can an animal pass to their offspring? and can it be predicted?
1/2 and it’s random
what is used to rank animals genetically?
progeny difference and transmitting ability
what are the predicted values of PD and TA called?
expected progeny difference (EPD) and predicted transmitting ability (PTA)
what industries is EPD used in?
meat production, beef cattle, swine, and sheep breeding
what industry is PTA used in?
dairy cattle breeding, milk production
what is gene combination value?
the part of the genotypic value that is due to gene combination effects, like dominance and epistasis
why is GCV not important to selection?
because individual genes, not gene combinations, survive segregation and independent assortment during meiosis, GCV can’t be transmitted from parent to offspring
what is producing ability?
represents the performance potential of an animal for a repeated trait
what are repeated traits?
traits for which the animal has multiple performance records during its lifetime, like milk production of a dairy cow
when are BV and GCV determined for an animal?
at birth and remain with the animal for its whole life
what are permanent environmental effects, or Ep?
some environmental factors which permanently affect the performance of the animal
give 2 examples of permanent environmental effects?
nutrition at developmental stages, permanent udder problem
what are temporary environmental effects, Et?
some environmental factors that do not affect performance permanently, like weather, forage quality, or management practices
what is producing ability a combination of?
genetics and permanent environmental effects, so PA = G + Ep, and G = BV + GCV
what is the overall expanded formula for producing ability?
PA = BV + GCV + Ep
what is the full expanded model for repeated traits?
P = u + BV + GCV + Ep + Et
why is producing ability important?
as a measure of the productive capacity, it usually determines many aspects of production, like how much dairy farmers feed their cows
what is the predicted value of producing ability?
most probable producing ability, or MPPA
what is the formula for the prediction of an animal’s next record, or P?
P = u + MPPA
