Additive genetic effects

Additive genetic effects

Fisher's Polygenic Model

Fisher's Fundamental Theorem

Additive genetic effects refer to the cumulative effect of individual genes on a phenotype, where the total genetic contribution to a trait is the sum of the effects of all alleles involved. This concept is fundamental in the study of quantitative genetics and is crucial for understanding the inheritance of complex traits.

Overview

In genetics, the phenotype of an organism is influenced by its genotype and the environment. The genotype consists of the alleles inherited from the parents, and these alleles can have different types of effects on the phenotype. Additive genetic effects are those where the contribution of each allele to the phenotype is independent of the presence of other alleles. This means that the effect of an allele is the same regardless of the genetic background.

Fisher's Polygenic Model

Ronald Fisher, a pioneer in the field of genetics, introduced the concept of additive genetic effects in his polygenic model. This model suggests that traits are controlled by many genes, each contributing a small amount to the overall phenotype. The polygenic model is particularly useful for explaining the inheritance of quantitative traits such as height, weight, and intelligence, which do not follow simple Mendelian inheritance patterns.

Fisher's Fundamental Theorem

Fisher's Fundamental Theorem of Natural Selection states that the rate of increase in fitness of a population is equal to the additive genetic variance in fitness. This theorem highlights the importance of additive genetic effects in the process of natural selection. It implies that the potential for a population to adapt to its environment is directly related to the amount of additive genetic variance present.

Importance in Breeding and Evolution

Additive genetic effects are crucial in the fields of animal breeding and plant breeding. Breeders select individuals with desirable traits to produce offspring with improved characteristics. Since additive effects are predictable and heritable, they are the primary focus in selection programs. In evolutionary biology, additive genetic variance is a key factor in the adaptive potential of populations.

Related pages

• Quantitative genetics
• Polygenic inheritance
• Heritability
• Natural selection

Gallery

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  Fisher's Polygenic Model
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  Fisher's Fundamental Theorem

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  Fisher's Polygenic Model
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  Fisher's Fundamental Theorem