Unit 3, Part 8 Flashcards
What is the difference between quantitative and qualitative traits?
Quantitative traits have continuous phenotypes and are often polygenic, while qualitative traits are typically categorical.
What are examples of quantitative traits?
- Height
- Weight
- Marbling
- Back fat
- Grain yield
- Some diseases
Define polygenic traits.
Traits controlled by many loci, each with a small individual effect.
List some economically important quantitative traits.
- Weight
- Milk production
- Marbling
- Back fat
- Grain yield
- Feed efficiency
What does the equation Phenotype = Genotype + Environment represent?
It illustrates how phenotype is influenced by both genetic and environmental factors.
What is variance in the context of quantitative genetics?
A statistical measure of spread, indicating how variable the data is.
What are the components of phenotypic variance?
- Genetic variance (VG)
- Environmental variance (VE)
What is genetic variance (VG)?
Variance in a trait due to genetics.
What is environmental variance (VE)?
Variance in a trait due to environmental factors.
What is the formula for phenotypic variance (VP)?
VP = VG + VE
What does narrow-sense heritability (h2) represent?
The proportion of phenotypic variance that is due to additive genetic variance.
What is the formula for narrow-sense heritability?
h2 = VA / VP
What does broad-sense heritability (H2) represent?
The proportion of phenotypic variance that is due to genetic variance.
What is the formula for broad-sense heritability?
H2 = VG / VP
What does the response to selection (R) measure?
The amount of change in a trait with one generation of selection.
What is the formula for response to selection?
R = h2 x SD
What does selection differential (SD) represent?
The difference in the parents’ phenotype from the average phenotype of the population they came from.
What is the significance of heritability estimates?
They indicate the degree to which alleles determine variation in a trait.
True or False: Heritability gives information about the mean of a trait.
False
How can heritability estimates change?
They can change with alterations in the environment.
What is the goal of a breeding program focused on average daily gain (ADG) in pigs?
To improve average daily gain in the herd.
What does the term ‘genetic by environment variance’ (VGxE) refer to?
Interactions between genotype(s) and the environment.
What is the impact of non-additive effects in genetic variance?
They are interactions between alleles that are not passed on in a predictable manner.
What does ‘dominance variance’ (VD) refer to?
Interactions at the same locus due to dominant and recessive gene action.
