Bioinformarics: different types of homologous genes

Bioinformarics: different types of homologous genes

The main purpose of phylogeny is to pick what we call Homologous genes and compare them to construct a phylogenetic tree of their history, according to their similarities.

Homologous genes are genes that derive from a common ancestor. To understand the homologous genes types and how exactly they derive, we have to know couple of things

* Speciation: is the phenomenon during which a common ancestor gives birth to two subgroups that slowly drift away from their common genetic makeup to become distinct species.

* Duplication: Means that within the same genome of the same species, the gene was duplicated, in this case, may be one of the genes remain the same with the same function, and the other may change.


Homologous genes have three types:

1- Orthologs: Orthologs are 2 genes that are separated by speciation, it means generally that 2 genes exist in 2 different species, but they were in the same common ancestor.

2- Paralogs: Paralogs are 2 genes separated by duplication, this means that the same gene in one genome was duplicated to 2 genes or more.

3- Xenologs: Xenologs result from Lateral Transfer between 2 species or organisms, a DNA transfer from species to another, like the transfer of a DNA sequence from a virus or bacteria to another species.


In bioinlformatics collecting these genes from Blast searches, and aligning them into a multiple sequence alignment is the main tool to construct a phylogenetic tree.

Any questions, you are welcome.