Term
| What is the genetic model? |
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Definition
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Term
| Define each of the variables P=G+E |
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Definition
P-phenotype
G-genotype/genetic value
E-environment |
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Term
| What are the categories when discussing environment and how are they different? |
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Definition
Macro-environment: affects entire group
Micro-environment: affects individuals |
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Term
| What are the two different types of environmental effects? |
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Definition
Permanent: affects individual remainder of life
Temporary: affects individual single production cycle |
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Term
| What is a contemporary group? |
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Definition
| a group of animals w/an EQUAL OPPORTUNITY to perform. (minimal environmental differences; same season, building, feed) |
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Term
| What are the factors that are considered when determining contemporary groups and why? |
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Definition
Number of sires: compare for selection; can select from among the best families and individuals for traits.
Sires in multiple groups: increases accuracy from more data on each sire family.
Number of offspring per sire: matter of accuracy
Born w/in short period and tested together: minimizes environmental effects |
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Term
| What are the optimal number of sires to compare at a time and the ideal number of offspring records for each? |
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Definition
3-4 sires
Approx. 40 offspring.
Both due to MC=MR |
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Term
| If all animals w/in a contemporary group can be tested, how should animals be selected for testing? |
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Definition
| At random to eliminate bias |
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Term
| Why do we use records adjustment factors? |
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Definition
To compare animals on an equal basis
Expand the contemporary group |
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Term
| What do we adjust records for and what are some examples? |
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Definition
Known and predictable sources of information
-Age
-Sex (of individual or offspring)
-Age of dam
-Parity of dam
-Lactation (dairy) |
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Term
| When dealing w/performance records, what should be asked about their origin? |
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Definition
| If there was any adjustment and how they were adjusted |
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Term
| As geneticists, why are we interested in environmental effects and their adjustments? |
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Definition
| In order to better remove/reduce the "environmental noise" and have a more accurate interpretation of genetically superior animals |
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Term
| Compare and contrast additive and multiplicative adjustment factors. |
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Definition
Additive: linear and adds by a constant
Multiplicative: exaggerates extremes; spreads out data |
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Term
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Definition
| a statistic taht estimates how much variation in a phenotypic trait is due to genetic variation among individuals. |
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Term
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Definition
| the proportion of the phenotype that is repeatable during the next production cycle |
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Term
| What is MPPA and why is it used? |
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Definition
| Most Probable Producing Ability: used to predict repeated performance |
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Term
| What is EBV and why is it used? |
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Definition
| Estimated Breeding Value: used to predict the value of the offspring |
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Term
| What is realized heritability? |
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Definition
| the amount of variation due to TRANSMITTABLE GENETIC EFFECTS |
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Term
| What are the two uses of heritablity? |
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Definition
to predict the potential response to selection (help choose traits for selection)
Prediction of breeding value to selected individuals |
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Term
| What is EBV and EPD and how are they different? |
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Definition
EBV: Estimated Breeding Value; the deviation from the average
EPD: Expected Progeny Value; the portion of the parent breeding value passed on to the offspring
EBV=EPD*2
EPD=PTA (Predicted Transmitting Ability) |
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Term
| What is the inbreeding coefficient and what is its use? |
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Definition
the percent of loci which have both alleles identical by descent.
Useful because animals w/more genes in common will have similar phenotypes (both positive and negative) |
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Term
| What is the relationship coefficient and what is its use? |
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Definition
the percent of alleles in TWO DIFFERENT INDIVIDUALS which are identical by descent.
Useful in selecting animals to breed across generations to prevent/manage inbreeding |
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Term
| In the Bx equation, what does h^2 mean? |
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Definition
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Term
| In the Bx equation, what does n mean? |
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Definition
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Term
| In the Bx equation, what does a mean? |
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Definition
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Term
| In the Bx equation, what does Rxy mean? |
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Definition
| Relationship of the source to the animal calculating |
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Term
| In the Bx equation, what does Rxx mean? |
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Definition
| Relationship between source animals |
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Term
| In the Bx equation, what does C^2 mean? |
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Definition
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Term
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Definition
| Mean of (source animal x or i; herd) |
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Term
| How is records adjustment used? |
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Definition
| (gain/day)[adjustment factor days] |
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Term
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Definition
| controlling reproduction of individuals w/in a population |
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Term
| Explain selection intensity. |
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Definition
| how hard a certain trait or performance level is selected for, ruling out less superior animals for breeding |
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Term
| Why is individual record the best single source of information? |
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Definition
| because it has an accuracy of 1 in the accuracy equation |
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Term
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Definition
| Best Linear Unbiased Prediction: uses all data available to predict EBV |
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Term
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Definition
| a measure of repeated performance of production. |
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Term
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Definition
| a prediction of the deviation above/below average production |
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Term
| What causes genetic correlation? |
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Definition
Pleiotrophy: same genes acting on several characters
Linkage: genes closely associated on chromosomes |
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Term
| When dealing w/multiple sources for breeding value information, why can't the breeding values be estimated for each source and then added together? |
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Definition
| relationships between individuals and sources as well as inbreeding coefficients are not taken into account |
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Term
| When would using a correlated source of information be more beneficial than measuring the trait itself? |
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Definition
When the trait is uneconomical to measure (feed consumption and conversion)
In instances of high correlation (pubertal teste size and maternal traits) |
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Term
| How is accuracy used in deciding breeding? |
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Definition
| Higher accuracy renders a lesser chance for deviation of the parent EBV, but with lower accuracy there is an equal chance to have offspring with a higher or lower EBV than possible with high accuracy |
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Term
| Why is it poor practice to multiply EPD by accuracy? |
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Definition
| Accuracy is already accounted for when determining breeding values |
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Term
| How can accuracy of an EBV be increased? |
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Definition
| by obtaining more offspring data |
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Term
| What are reference sires and what is their purpose? |
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Definition
Reference sires: serve as benchmarks to connect herds.
More reference sires = more connectivity and more accuracy |
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