Genetic Model for Qualitative Traits Flashcards
What are simply inherited traits?
traits affected by one or few genes
What are other names for simply inherited traits?
- qualitative
- monogenic
- monofactorial
What are examples of simply inherited traits?
coat color, presence of horns, and genetic defects like spider syndrome in sheep
How are phenotypic traits of simply inherited traits shown?
placed into categories
How does the environment affect simply inherited traits?
little effect
What are polygenic traits?
traits affected by many genes (no single gene having an overriding effect)
What are examples of polygenic traits?
growth rate, milk production, birth weight
How are polygenic traits generally described?
in numbers
How are polygenic traits expressed?
quantitative or continuous in their expression
What is an exception to how polygenic traits are typically expressed? Why?
Dystocia, it is affected by many genes but the phenotype is described in categories
Are polygenic traits affected by the environment?
yes
What is the basic model for quantitative traits?
P = µ + G + E
What does P represent?
phenotypic value of an animal for a given trait
What does µ represent?
population mean or average phenotypic value for the trait of all animals in the population
What does G represent?
the genotypic value of the animal for the trait
What does E represent?
the effect of the environmental factors on the phenotype of the animal
How are G and E expressed?
as deviations from the mean of the population
What do the mean of G and the mean of E equal?
zero
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
Is G directly measurable?
no
is P directly measurable?
yes
What is the genotypic value the sum of?
breeding value and gene combination value
What is the formula for genotypic value?
G= BV + GCV
What is breed value also called?
additive gene value
What is breeding value?
the sum of the effects of individual genes independent of the effects of dominance or epistasis
What are the effects of individual genes in terms of breeding value called?
independent gene effects or additive gene effects
What is breeding value considered as?
a parental value
What is parental value?
the value of an individual as a contributor of genes to the next generation
What must be done before animals are selected as parents of the next generation?
estimate their breeding values and choose those with the best breeding values
What is GEBV?
gene enabled breeding value
What does an individual transmit to its offspring?
a sample composed of a random half of its genes to each of its offspring
What is used to rank animals?
Progeny Difference or Transmitting Ability
PD=TA=?
1/2 BV
What type of concept are Progeny Difference and Transmitting ability?
practical
What are Progeny Difference and Transmitting Ability defined as?
the expected difference between the mean performance of the progeny of a parent and the mean performance of the progeny of all parents in the population
What is the formula for Progeny Difference/Transmitting Ability
PDi = TAi = µ (offspring of parent i) – µ (offspring of all parents )
What can Progeny Difference and Transmitting Ability be predicted with?
performance data
What is the predicted value of progeny difference?
EPD (expected progeny difference)
What is the predicted value of Transmitting Ability?
PTA (predicted transmitting ability)
What is EPD used for?
beef cattle, swine, and sheep
What is PTA used for?
dairy cattle
What can BV be viewed as?
the sum of the additive effects of the genes inherited from the sire (father) and the additive effects of the genes inherited from the dam (mother)
What is the formula for BV of offspring?
(BV sire + BV dam) / 2
What is GCV part of?
the genotypic value that is due to gene combination effects (dominance and epistasis)
Why can’t GCV be transmitted from parent to offspring?
because individual genes and not gene combinations survive segregation and independent assortment during meosis
Is GCV important to selection?
no
Why is GCV not important for selection?
because GCV cannot be transmitted from parent to offspring
Can GCV be transmitted from parent to offspring?
no
What is the full genetic model for repeated traits?
P = µ + BV+ GCV + E
What is producing ability (PA) important for?
repeated traits
What are repeated traits?
traits where the animals has more than one performance record during its lifetime
What are examples of repeated traits?
milk production, offspring weight, laying rate, litter size, litter weight
What does producing ability (PA) represent?
the performance potential of an animal for a repeated trait
What is producing ability (PA) a function of?
all those factors which permanently affect the performance potential of the animal
What is determined at conception and remains with the animal during its entire life?
genotypic value and its components
What are the components of the genotypic value?
BV and GCV
What are the two types of environmental effects?
permanent and temporary
What are permanent environmental effects represented by?
Ep
What are permanent environmental effects?
permanently affect performance
What is producing ability (PA) affected by (idk if thats right)?
environment
What are examples of permanent environmental effects?
- nutrition at early development stages affects the ability of beef and dairy cows to produce milk permanently
- a permanent problem in udder will affect milk during all productive life of cow
What are temporary environmental effects represented by?
Et
What are examples of temporary environmental effects?
forage quality, weather conditions, and some management practices`
What are temporary environmental effects?
factors that vary from season to season or year to year and so they do not influence different records in the same way
What is producing ability a combination of?
genetic and permanent environmental effects
What is the formula for producing ability?
PA = G + Ep or PA=BV + GCV + Ep
Who is producing ability important to?
commercial producers
Why is producing ability important to commercial producers?
it is used as a measure of productive capacity
How do dairy farmers feed their cows?
according to their producing ability
What is the predicted value of PA called?
Most Probable Producing Ability (MPPA)
What is the formula for prediction of the animal’s next record?
P=µ + MPPA