For a cell, normally, when it divides into two daughter cells, its entire genome is duplicated. But, as has been the theme for a while, things do not always go the way they are intended to. Random changes of events cause different things to occur, and in some cases, the effects prove beneficial to a species, while in others, the effects can be deleterious. In the case of cell division of this sort, sometimes an accident can cause inappropriate duplication of part of the genome of a cell. In the chain of events, what this leads to is retention of original and duplicate segments within a single cell. Then, one of the two gene copies is able to mutate and take on a specific role in the same cell, different from the role of the first gene copy. It becomes specialized to perform this function. This process continues repeatedly over time, and what is created is a gene family, which began with a single gene, which late gave rise to a family of genes that can all be found in one genome (Alberts et al. 2014).
This process of duplication and divergence results in all of the individuals in a particular species having many different variants of a primordial gene. This is not the same as when two different species of organism splits into two separate lines of descent. There are terms for these two processes, which we will use to distinguish one from the other. The case that we have discussed up until this point, wherein an accident results in the inappropriate duplication of a part of the genome, describes paralogs. Paralogs are related genes that have been derived in the way described, via a duplication event within just one genome. On the contrary, orthologs also exist, but are not to be confused with paralogs. Orthologs, on the other hand, are genes of two separate species that are derived from the same ancestral gene in the last common ancestor of those two species. Genes that are orthologs, over time with evolution, will likely have corresponding functions in the two sister species, or functions that are analogous to one another. Both paralogs and orthologs fall under the category of homologs, which describes in general, genes that are related by descent, therefore encompassing both groups discussed (Alberts et al. 2014).
A prospective medical student, looking to help others succeed.