Which of the following is true regarding Crossbreeding A. The mating of sires of one breed or breed combination to dams of another B. To produce hybrid vigor or heterosis C. Hybrid vigor is an increase in performance of crossbred or hybrid D. All

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2. Which of the following is true regarding Crossbreeding?

• A. The mating of sires of one breed or breed combination to dams of another. This is a correct definition of crossbreeding.
• B. To produce hybrid vigor or heterosis. This is a primary goal of crossbreeding.
• C. Hybrid vigor is an increase in performance of crossbred or hybrid. This is a correct definition of hybrid vigor.
• Since all statements A, B, and C are true, option D is the correct choice.

The final answer is $\boxed{\text{D}}$

3. Simply-inherited traits_____

• A. Affected by many genes. This describes polygenic or quantitative traits.
• B. Traits are clearly affected by environment. This also describes quantitative traits.
• C. Only a single locus or, at most, a few loci are involved in their expression. This is the defining characteristic of simply-inherited traits.
• D. All. This is incorrect as A and B are false.

The final answer is $\boxed{\text{C}}$

4. Heritability in the broad sense ($H^2$)_____

• A. Is a measure of the strength of the relationship between performance (phenotypic values) and genotypic values. This is the correct definition of broad-sense heritability, which is the proportion of phenotypic variance due to total genetic variance.
• B. Examples of repeated traits include milk yield in dairy animals, litter size in swine, and fleece weight in sheep. These are examples of traits for which repeatability is calculated, not heritability.
• C. It can be determined for any trait in which individuals commonly have more than one performance record. This describes repeatability, not heritability.
• D. All. This is incorrect as B and C are false.

The final answer is $\boxed{\text{A}}$

5. As a correlation, repeatability ranges from_____
Repeatability is a correlation coefficient that measures the consistency of repeated measurements on the same individual. In quantitative genetics, repeatability values range from 0 to 1 because it is a ratio of variance components, which are always non-negative. However, the general mathematical range for any correlation coefficient is from $-1$ to 1. Given the options, and acknowledging that repeatability cannot be negative in a biological context, option A represents the general mathematical range for a correlation.

The final answer is $\boxed{\text{A}}$