Cattle breeders would like to improve the protein content and but...

Question

Cattle breeders would like to improve the protein content and butterfat content of milk produced by a herd of cows. Narrow sense heritability values are 0.60 for protein content and 0.80 for butterfat content. The average percentages of these traits in the herd and the percentages of the traits in cows selected for breeding are as follows.

Trait Herd Average Selected Cows
Protein content 20.2% 22.7%
Butterfat content   6.5%   7.4%

Which trait is likely to be the most responsive to artificial selection applied by the cattle breeders through selection of cows for mating?

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. What does a low value of narrow sense heritability suggest about the influence of genetics and the environment on a trait. The answer options are a genetics play a more significant role in the expression of the trait B. The trait is more likely to respond to selective breeding. C. The trait is influenced more by environmental factors and d both genetics and the environment have an equal influence on the trait. Now recall that irritability can be expressed as broad or narrow and the definition of narrow narrow sense heritability is the phenotypic variability due to only additive effects of genes and not all genetic factors. Now, it's expressed with the value between zero and one. The larger value is or the closer to one indicates the phenotypic variability is due more to additive effects of the genes and a lower value, narrow sense heritability indicates phenotypic variability is not due to the additive effects of genes. So let's go ahead and look at those answer options again. Now option a, if genetics played a more significant role in the expression of a trait, we would expect to have a high narrow sense heritability. So we can eliminate option A. Option B, the trait is more likely to respond to selective breeding. We would expect this as well with a high narrow sense heritability because a high sense, narrow sense heritability is going to show the greater response to selection since it means more genetic factors influence the phenotype. So option B is also incorrect. Now, option D we should know is also an incorrect statement because it states that both genetics and the environment have an equal influence on the trait. And remember when you have a lower value, it's that the phenotypic variability is not due to additive effects of the genes. So you would have more environmental factors influencing the trait. So option D is also incorrect. The correct answer is option C, the trait is influenced more by environmental factors. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.

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