Question

If the narrow sense heritability of a trait is 0, what does this mean? Does this mean a trait is entirely determined by environment? Explain all the contributions to total phenotypic variance.

Answer 1

The narrow-sense heritability is the ratio of additive genetic variance to the total phenotypic variance. So narrow sense heritability of a trait zero means additive genetic variance is zero. This condition means trait is entirely determined by environment because Additive genetic variance involves the inheritance of a particular allele from your parent and this allele's independent effect on the specific phenotype. so if there is no inheritance from the parent then the trait is determined by the environment.

Phenotypes are traits or characteristics of an organism that we can observe, such as size, color, shape, capabilities, behaviors, etc. phenotypes can be caused by genes, environmental factors, or a combination of both. Total Phenotypic variation, then, is the total variability in phenotypes that exists in a population.An organism's phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes.