Genetic Model for Quantitative Traits

Question 1

what are simply inherited traits?

Answer 1

affected by one or few genes, phenotypes placed into categories

Question 2

give 3 examples of simply inherited traits

Answer 2

coat color, presence of horns, certain genetic defects

Question 3

how do environmental factors affect simply inherited traits?

Answer 3

very little

Question 4

what are polygenic traits?

Answer 4

affected by many genes (no gene having an overriding effect), generally described in numbers, typically quantitative or continuous in their expression

Question 5

what is an exception to polygenic traits?

Answer 5

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

Question 6

are polygenic traits effected by the environment?

Answer 6

yes, very

Question 7

what is the most basic model for quantitative traits?

Answer 7

P = mew + G + E

Question 8

what is genotypic value?

Answer 8

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

Question 9

what two values is genotypic value (G) the sume of?

Answer 9

breeding value (BV) and gene combination value (GCV)

Question 10

what is breeding value also called?

Answer 10

additive genetic value

Question 11

what is breeding value?

Answer 11

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

Question 12

what must be done before selecting animals to be parents?

Answer 12

their breeding values must be estimated and the best BV must be chosen to get the best result

Question 13

how much of their genes can an animal pass to their offspring? and can it be predicted?

Answer 13

1/2 and it’s random

Question 14

what is used to rank animals genetically?

Answer 14

progeny difference and transmitting ability

Question 15

what are the predicted values of PD and TA called?

Answer 15

expected progeny difference (EPD) and predicted transmitting ability (PTA)

Question 16

what industries is EPD used in?

Answer 16

meat production, beef cattle, swine, and sheep breeding

Question 17

what industry is PTA used in?

Answer 17

dairy cattle breeding, milk production

Question 18

what is gene combination value?

Answer 18

the part of the genotypic value that is due to gene combination effects, like dominance and epistasis

Question 19

why is GCV not important to selection?

Answer 19

because individual genes, not gene combinations, survive segregation and independent assortment during meiosis, GCV can’t be transmitted from parent to offspring

Question 20

what is producing ability?

Answer 20

represents the performance potential of an animal for a repeated trait

Question 21

what are repeated traits?

Answer 21

traits for which the animal has multiple performance records during its lifetime, like milk production of a dairy cow

Question 22

when are BV and GCV determined for an animal?

Answer 22

at birth and remain with the animal for its whole life

Question 23

what are permanent environmental effects, or Ep?

Answer 23

some environmental factors which permanently affect the performance of the animal

Question 24

give 2 examples of permanent environmental effects?

Answer 24

nutrition at developmental stages, permanent udder problem

Question 25

what are temporary environmental effects, Et?

Answer 25

some environmental factors that do not affect performance permanently, like weather, forage quality, or management practices

Question 26

what is producing ability a combination of?

Answer 26

genetics and permanent environmental effects, so PA = G + Ep, and G = BV + GCV

Question 27

what is the overall expanded formula for producing ability?

Answer 27

PA = BV + GCV + Ep

Question 28

what is the full expanded model for repeated traits?

Answer 28

P = u + BV + GCV + Ep + Et

Question 29

why is producing ability important?

Answer 29

as a measure of the productive capacity, it usually determines many aspects of production, like how much dairy farmers feed their cows

Question 30

what is the predicted value of producing ability?

Answer 30

most probable producing ability, or MPPA

Question 31

what is the formula for the prediction of an animal’s next record, or P?

Answer 31

P = u + MPPA