2 Domestication, Breeding and Genetics Flashcards
(15 cards)
What is the selection differential (S) in animal breeding?
It’s the difference between the mean performance of selected animals and the population average. Higher S leads to more genetic gain.
What two factors influence the selection differential (S)?
1) Variation in phenotype and 2) the proportion of animals selected.
What is the generation interval (L) and why does it matter?
It’s the average age of parents when offspring enter the breeding population. A shorter L results in faster genetic improvement.
What shape does the performance distribution of quantitative traits usually follow?
A normal (bell-shaped) distribution.
What are the three main factors influencing genetic gain and selection response?
Selection differential (S) or intensity (i), heritability (h²), and generation interval (L).
Summarize three key takeaways for maximizing genetic improvement.
Higher selection intensity = faster genetic gain
Shorter generation intervals = faster improvement
Understanding heritability = more accurate predictions
Why are relative performance records important in selection?
Because related animals share genes, these records help estimate genetic merit or EBV.
What proportion of genes do parents and offspring share? What about siblings?
Parents and offspring share 50% of their genes. Siblings and other relatives share variable proportions due to recombination.
What is an Estimated Breeding Value (EBV)?
It’s a prediction of an animal’s additive genetic merit, based on phenotypic and performance data, expressed in units (e.g., kg).
What are the four main sources of information for estimating EBVs?
Ancestors (pedigree selection)
The animal itself (performance test)
Siblings (sib selection)
Progeny (progeny test)
What factors affect the accuracy of selection (r)?
Trait heritability (h²)
Source of information (which relative)
Number of relatives measured
What is the purpose of using repeated records in genetic evaluation?
For traits measured multiple times (e.g., milk yield), repeatability helps assess consistency; benefit decreases as h² increases.
What is correlated response to selection and what causes it?
It’s a change in one trait due to selection on another genetically correlated trait, caused by pleiotropy or linkage disequilibrium.
How is multi-trait selection used in breeding?
It leverages genetic correlations between traits to improve multiple traits simultaneously, balancing economic merit.
What three factors are crucial in predicting selection response?
Accuracy of selection
Trait heritability
Consideration of correlated responses
