- As mentioned, simply-inherited and polygenic traits are equally subject to the same Mendelian and non-Mendelian inheritance forces. And both can have gene and genotypic frequencies shifted by selection and mating systems. But while it is often straightforward to observe the effect of a simply-inherited trait owing to the small number of genes involved, this isn’t the case with polygenic traits. It is often not even known how many genes are involved in a particular polygenic trait, nor what the effect of each may be. It is because of this complexity that breeders must take very different approaches when working with simply-inherited and polygenic traits.
- While — for the most part — there are differences between simply-inherited and polygenic traits, they also share much in common. Both types of trait are still determined by genes and inheritance.
- The word trait, you may recall, is often used interchangeably with phenotype, but they are not the same thing at all. A trait is something that can be measured or observed, for example temperament, colour or wool staple length/year. A phenotype is the value of the trait: ‘aggressive’, ‘brindle’ or ‘120mm’. Traits fall into two categories: simply-inherited and polygenic.