Estimation of Additive, Non-Additive Genetic and Environmental Variances in Animal Population | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Estimation of Genetic and Environmental Variances in Animal Population

• The additive variance, representing breeding values, is crucial as it primarily determines similarities among relatives and influences genetic properties and response to selection.
• It's the only component easily estimated from population observations, separating additive genetic variance from non-additive genetic and environmental variances.

• Resemblance between relatives, like offspring and one parent, allows estimating additive genetic variance.
• For instance, the covariance between offspring and one parent's breeding value indicates half the parent's breeding value.

• Expressing variance in terms of gene frequency for a single locus with two alleles.
• Genotypic values are measured as deviations from the population mean.
• By observing phenotypic covariance among relatives, one can estimate additive genetic variance.

Calculating Additive Variance

• The additive variance, related to breeding values, is calculated by squaring values, multiplying by genotype frequencies, and summing over genotypes.
• It's crucial in understanding genetic properties within populations.

Understanding Genetic Variance:

• Genetic variance refers to the variability in traits that can be attributed to genetic differences among individuals.
• It is crucial in understanding the heritability of certain traits and how they are passed down through generations.
• Genetic variance can be broken down further into additive and dominance components.

Additive Variance:

• Additive variance represents the genetic variance contributed by additive effects of alleles.
• When there is no dominance at a specific locus, the additive variance simplifies to a formula involving allele frequencies and a parameter 'a'.
• For instance, with complete dominance, the additive variance can be expressed differently based on the genetic makeup of the population.

Dominance Variance:

• Dominance variance accounts for the genetic variance resulting from interactions between alleles at the same locus.
• It plays a significant role in determining the phenotypic expression of traits, especially in the presence of dominant or recessive alleles.
• Dominance variance can be calculated based on the dominance deviation and gene frequencies in a population.

Environmental Variance:

• Environmental variance encompasses variations in traits that are not of genetic origin.
• Factors such as nutrition, climate, and maternal effects can contribute to environmental variation.
• It is crucial to minimize environmental variance in genetic studies to improve precision and accuracy.
• Estimating environmental variance involves studying the repeatability of traits through multiple measurements within and between individuals.