Question

A trait, such as height, has high heritability because much of the variation between individuals is the result of genetic variation. However, not all of the variation for height in a population can be attributed to genetic variation alone.

Why does genetic variation not always determine the differences in a given trait between individuals?
-Independent assortment leads to new combinations of genes.
-Changes in the environment can influence the expression of a gene.
-Genetic drift changes the frequency of genes within a population.
Random mutations lead to the generation of new alleles.

Answer 1

Genetic variation is one factor determining traits like height, but environmental factors, genetic drift, and random mutations also contribute to phenotypic differences. Heritability measures the amount of variation due to genetics, but many traits are polygenic and influenced by multiple genes and the environment.

Step-by-step explanation:

Genetic variation does not always determine the differences in a given trait between individuals because of other influential factors. One such factor includes environmental influences on gene expression. For example, changes in the environment can affect height, where access to good nutrition can enable an individual to attain a taller stature, regardless of the potential height determined by their genes.

Furthermore, genetic drift can alter the frequency of genes within a population independently of any adaptive advantages, often due to random chance events. Additionally, random mutations can create new alleles, introducing new genetic variation that can underpin phenotypic differences.

Heritability describes the proportion of phenotypic variation attributable to genetic differences in a population. However, it is crucial to recognize that most traits, including height, are polygenic traits, which are influenced by multiple genes and not a single gene pair. The complex interplay of various genes combined with environmental factors means that not all phenotypic variation can be predicted by genetics alone.