Question

Question 2. The terms homolog encompasses both orthologs and paralogs. Define each of these terms to distinguish them. How can you test (a) computationally and (b) experimentally if two genes are orthologous to each other?

Answer 1

Orthologs are genes in different species evolved from a common ancestral gene.The function of gene product is similar in different species which retain the functional characteristics of the ancestral gene. Paralogs are gene copies created by a duplication event within the genome of same species.Each copy may assume a different function over time

Computational method to identify if two genes are orthologous to each other:The basic procedure involves collecting gene sequence in two species and comparing the to one another( through Clustal omega, CD-HIT, etc). If genes from two species identify each other as their closest partners then they are considered orthologs. They will both produce the same results in very closely related species. Proteinortho is a specialized tool to detect orthologous genes within different species that works on the similar principle.

Experimental method to identify if two genes are orthologous to each other:Let gene A from species A be mutated.Now introduce a genetically engineered clone( in species A) carrying wild type B gene placed under the promoter of gene A.If the clone encodes a functional protein that is able to restore the wild type phenotype in species A, then the the two genes are likely to be orthologs. This because they would be closely related and carry out similar function. A similar experiment in which is carried out in species B will also give the same results.