Genes on the same autosome
Autosomal linkage occurs when two or more genes are located on the same autosome. These genes are described as linked.
Dihybrid crosses normally assume that the two genes assort independently during meiosis. Linked genes do not follow this assumption because alleles carried together on the same chromosome tend to remain together during inheritance.
This means that the original combinations of alleles carried on the parental chromosomes tend to be inherited together, reducing the number of different combinations expected compared with independent inheritance.
Representing linked alleles
Linked alleles can be grouped in brackets to show which alleles occur on the same chromosome.
For example, an individual carrying T and G together on one chromosome and t and g together on its homologous chromosome can be written:
In the simplified linked prediction, the parental allele combinations are therefore TG and tg, rather than the four gamete combinations expected from independent inheritance.