Pseudoalleles

Pseudoalleles are genes that are located very close to each other on a chromosome and are often inherited together, but they do not have the exact same DNA sequence. While they may code for similar functions or proteins, their slight differences can lead to distinct phenotypes. Historically, the concept of pseudoalleles arose from genetic experiments where mutations in what appeared to be a single gene locus could be resolved into two or more closely linked but functionally distinct units. These units could recombine with each other at a low frequency, indicating they were separate but adjacent genetic elements. This phenomenon was crucial in understanding gene structure and the concept of the cistron, a unit of genetic function defined by the cis-trans test. Modern molecular genetics can often explain pseudoalleles as separate genes within a gene family that have undergone duplication and divergence, or as distinct regulatory elements acting on a nearby gene. The close proximity and shared ancestral origin contribute to their tendency to be inherited as a unit, hence the term "pseudo" or "false" allele, as they are not identical alleles of the same gene but rather separate entities that behave similarly in inheritance.