23: Genetic Change and Genetic Prediction

Question 1

Genetic Prediction is the area of animal breeding concerned with what?

Answer 1

Measurement of data, statistical procedures, and computational techniques for predicting breeding values and related values

Question 2

Four methods for genetic prediction

Answer 2

• mass selection
• selection index
• best linear unbiased prediction (BLUP)
• genomic selection

Question 3

What is mass selection

Answer 3

Selection based solely on an individual’s own phenotype
Animals ranked based on their performance (no pedigree info, performance data of sibs, parents, progeny)

Question 4

Mass selection selects members of breeding stock exhibiting…

Answer 4

desirable qualities, or eliminates those showing undesirable ones

Question 5

Mass selection increases the occurrence of…

Answer 5

desirable genes in a population

Question 6

How does mating work in mass selection

Answer 6

Animals with superior characteristics are selected and allowed to mate at random

Question 7

When will results from mass selection be the best?

Answer 7

With high heritability of the trait (phenotype is a good indicator of genotype)

Question 8

Why is mass selection usually not the choice?

Answer 8

We have other sources of information, such as performance of relatives (dam, sire, siblings, progeny)
More info = more accurate EBV

Question 9

What is selection index

Answer 9

Linear combination of various kinds of phenotypic information and appropriate weighting factors

Question 10

What sources of information are used for selection index

Answer 10

Individual’s own performance record, pedigree data, progeny data

Question 11

Selection indexes should only be used for…

Answer 11

genetic prediction when performance data comes from contemporary groups thought to be genetically similar

Question 12

What is a contemporary group

Answer 12

A group of animals that have experienced a similar environment with respect to the expression of a trait

Question 13

Factors affecting the accuracy of selection index

Answer 13

Number of records, heritability of the trait, pedigree relationship

Question 14

What is the Best Linear Unbiased Prediction (BLUP)

Answer 14

Extension of selection index methodology that requires intensive computation
Allows the use of phenotypic info of genetically different contemporary groups (diff farms and herds)

Question 15

BLUP is the preferred method for…

Answer 15

large-scale genetic evaluation/prediction using performance records collected from the field

Question 16

The BLUP model accounts for…

Answer 16

differences in the mean BVs of contemporary groups

Question 17

BLUP accounts for…

Answer 17

selection over time and accepts non-random mating of sires and dams

Question 18

BLUP can be thought of as a …

Answer 18

family of statistical models, including various genetic and environmental effects

Question 19

What is Animal Model

Answer 19

genetic statistical model that combines phenotypic information of related animals to achieve a better estimate of the breeding value for the animal

Question 20

Important advantages of the Animal Model

Answer 20

1. Dont necessarily need a record from each and every animal to be able to estimate its BV
2. Even if we have a phenotype, the extra info on related animals increases the accuracy of EBV

Question 21

What is genomic selection

Answer 21

Based on estimation of detailed associations between a very dense set of genetic markers (SNPs) and phenotypes on a select group of animals (reference population)

Question 22

Factors affecting accuracy of genomic selection

Answer 22

• trait heritability
• number of SNPs (higher better)
• population size (large better)
• genetic relationship between populations (closer relationship = better estimate of SNP effects)

Question 23

Benefits of genomic selection

Answer 23

• Decrease generation interval due to estimation of BVs for young animals before they have their own performance
• Reduce need for phenotyping for hard/expensive to measure phenotypes

Question 24

Genomic selection useful for selection of traits that are…

Answer 24

• very difficult or expensive to measure
• expressed later in life
• lowly heritable
• measured in only one sex

Question 25

Why do reference populations for genomic selection need to be updated on a regular basis

Answer 25

Associations between SNP and phenotype may be lost across generations

Question 26

Genomic estimated breeding value (GEBV) estimates…

Answer 26

the effect of each SNP marker and its association with the phenotypes economically important traits