What is a trait?

Meet the Glimmerbeast — a made-up creature we will breed to learn how inheritance works. The Glimmerbeasts and their authored traits are fictional; the inheritance principles are real. No real organisms are bred here.

A trait is an observable feature: coat colour, ear shape, tail length. Each trait is controlled by a gene, and a gene comes in variant forms called alleles.

A Glimmerbeast carries two alleles for each trait — one from each parent. We write alleles as letters: a capital letter for a dominant allele (e.g. C) and a lowercase letter for a recessive allele (e.g. c).