Quantitative traits are those that show continuous variability. A botanist measu
ID: 16932 • Letter: Q
Question
Quantitative traits are those that show continuous variability. A botanist measured the seed weight (a quantitative trait) and estimated its narrow-sense heritability of seed mass in three widely separated Phlox populations.
Population Mean Seed Mass(mg) narrow-sense heritability (h2)
A 15 0.60
B 12 0.65
C 17 0.58
a) Explain what narrow-sense heritability demonstrates and how the researcher might have obtained the values.
Despite the fact that the heritabilities were high and approximately equal, we cannot conclude that the differences in seed weight between the populations are largely due to genetic differences. Why? What experiment could be done to determine if there is a genetic component to the differences among populations?
Explanation / Answer
a) Explain what narrow-sense heritability demonstrates and how the researcher might have obtained the values. Narrow sense heritability only measures additive genetic variance: (Va/Vp). Additive variance primarily determines the resemblance between parents and offspring. The researcher can compare the parental phenotypes to the offspring phenotypes. Since narrow-sense heritability equals the regression coefficient (b). If the researcher graphs the values of the parent vs. the child they can determine if there is no relation between parent and offspring (b=0), if the offspring phenotype is the same as the parental phenotype (b=1), or if both genes and environment contribute to the differences in phenotype (b=.5). b. Despite the fact that the heritabilities were high and approximately equal, we cannot conclude that the differences in seed weight between the populations are largely due to genetic differences. Why? What experiment could be done to determine if there is a genetic component to the differences among populations? You cannot conclude that the differences in seed weight between the populations are largely due to genetic differences because the value of heritability for a characteristic is specific for a given population in a given environment.