Question

(a) H₂ and H₂ can be calculated as follows: For back fat: broad-sense = H₂ = 0.398, narrow-sense = H₂ = 0.276. For body length: Broad-sense = H₂ = 0.504, Narrow-sense = H₂ = 0.223. (b) For a trait that is quantitatively measured, the relative importance of genetic versus environmental factors may be formally assessed by examining the heritability index (H₂ or broad heritability). In animal and plant breeding, a measure of potential response to selection based on additive variance is termed narrow-sense heritability (H₂). A relatively high narrow-sense heritability is a prediction of the impact selection may have in altering an initial randomly breeding population. Therefore, of the two traits, selection for back fat would produce more response.

Answer 1

Heritability involves understanding the genetic basis of traits in a population. Higher narrow-sense heritability for a trait suggests a greater potential response to selective breeding, which, in the given example, indicates that back fat may be more responsive to selection than body length.

Step-by-step explanation:

The question relates to the concepts of heritability, genetics, and Mendelian laws. Heritability is the fraction of population variation that can be attributed to its genetic variance. The broad-sense heritability (H²) includes all genetic variance, while the narrow-sense heritability (h²) focuses on additive genetic variance alone, which is directly relevant to the response to selection in breeding.

Considering the plant breeding experiment in the question, based on Mendelian laws, we expect independent assortment and a 9:3:3:1 ratio for different trait combinations. The observed ratio in an actual experiment can then be compared to the expected values to assess consistency with Mendelian inheritance. If the observed ratio is close to the expected, it suggests that the traits are indeed inherited in a manner consistent with Mendel's laws.

In the practical example provided, where specific traits such as back fat and body length are measured, the provided heritability values indicate how much selection could change the traits. A higher narrow-sense heritability for back fat suggests that selection for this trait in animal breeding would likely be more effective than selection for body length, under the assumption that these heritability values remain consistent across generations.