[PDF] O RGANISMES DONT LES FORMATIONS ONT ETE HOMOLOGUEES

What is a homologous structure?

So different functions but same ancestry. Such structures, which have different functions, but same ancestry, we call them homologous, homo-- logous structures. Or homologous function. I just write homologous, okay? So what's important is that the word "homo", homo means same. Same. Same what? Same ancestors, and that's important. Same ancestor.

When are homologous sequences orthologous?

Homologous sequences are orthologous if they are descended from the same ancestral sequence separated by a speciation event: when a species diverges into two separate species, the copies of a single gene in the two resulting species are said to be orthologous.

Are orthologs and paralogs homologs?

On to the biology. Homology is the blanket term, both ortho- and paralogs are homologs. So, when in doubt use "homologs". However: Orthologs are homologous genes that are the result of a speciation event. Paralogs are homologous genes that are the result of a duplication event.

How do homologous chromosomes recombinate?

Lastly, homologous chromosomes take part in a process known as homologous recombination during the formation of gametes. This process is also known as “crossing over”, because parts of the homologous chromosomes are exchanged when they come into close contact.