Question

Differentiate between Broad-sense heritability and Narrow-sense heritability.

Answer 1

Hint: Heritability is a statistic used in breeding and genetics that estimates the degree of variation in a phenotypic trait in a population. It measures how much of the variation of a trait can be attributed to the variation of hereditary factors, as opposed to variation of environmental aspects.

Complete answer:
Heritability is indicated as H2 = Vg divided by Vp, where H is the heritability estimate, Vg the variation in genotype, and Vp the variation in phenotype. Heritability calculates range in value from 0 to 1. If H = 1, then all differences in a population is due to differences or variation between genotypes (i.e., there is no environmentally caused variation). If H = 0, there is no heritable variation; in this case, all differences in the population appear from differences in the environments experienced by individuals.
1Broad-sense heritability: It is the ratio of genotypic variance to the total phenotypic variance.
2.It is less reliable.
3.For e.g.: when dealing with segregated generations. It is valid mostly for homozygous lines.
 Narrow-sense heritability - It is the ratio of additive genotypic variance to the total phenotypic variance.
4.It is a more reliable standard as it is based on breeding values.

Note: Populations depending on the partitioning of observed variation into components that analyse unobserved genetic and environmental aspects. In other words, experimenters recognize that heritable and/or environmental variation exists, but they may not be in a situation to analyse either directly. However, this does not prevent them from being able to estimate the relative impacts of both genes and the environment on phenotype. Here, heritability can be estimated from experimental data on the observed and expected likeness between relatives.