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19 terms

Factors Affecting the Rate of Genetic Change

Chapter 10
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Key Equation
The equation relating the rate of genetic change resulting from selection to four factors: accuracy of selection, selection intensity, genetic variation, and genetic interval
Accuracy of Selection
"Accuracy of breeding value prediction" a measure of the strength of the relation
Selection Intensity
A measure of how "choosy" breeders are in deciding which individuals are selected.
Genetic Variation
Variability of breeding values within a population for a trait under selection
Generation Interval
The amount of time required to replace one generation with the next. The shorter the generation interval, the faster the rate of genetic change.
Rate of Genetic Change or Response to Selection
The rate of change in the mean breeding value of a population caused by selection.
Accuracy of Selection
The correlation between true breeding values and their predictions for a trait under selection.
Selection Criterion
An EBV, EPD, phenotypic value, or other piece of information forming the basis for selection decisions.
Selection Intensity
The difference between the mean selection criterion of those individuals selected to be parents and the average selection criterion of all potential parents, expressed in standard deviation units.
Selection Differential
The difference between the mean selection criterion of those individuals selected to be parents and the average selection criterion of all potential parents, expressed in units of the selection criterion.
Truncation Selection
Selection on the basis of a distinct division in the selection criterion (point of truncation) above which individuals are kept and below which they are rejected
Proportion Saved (p)
The number of individuals chosen to be parents as a proportion of the number of potential parents
Generation Interval (L)
The average age of parents when their selected offspring are born.
Closed Population
A population that is closed to genetic material from the outside
Genetic Trend
Change in the mean breeding value of a population over time
Phenotypic Selection Differential (S)
The difference between the mean performance of those individuals selected to be parents and the average performance of all potential parents, expressed in units of the trait.
Progeny Test
A test used to help predict an individual's breeding values involving multiple matings of that individual and evaluation of its offspring
Replacement Rate
The rate at which newly selected individuals replace existing parents in a population
Selection Risk
The risk that the true breeding values of replacements will be significantly poorer than expected