Question

Which of the given statements is incorrect about Clusters of orthologous groups?

(a) Using the protein from one of the organisms to search the proteome of the other for high-scoring matches should identify the ortholog as the highest- scoring match, or best hit

(b) When entire proteomes of the two organisms are available, orthologs may be identified

(c) a pair of orthologous genes in two organisms share so much sequence similarity that they may be assumed to have arisen from a common ancestor gene

(d) each of the orthologs belongs to a family composed of  paralogous sequences but irrelevant or not related to each other

This question was addressed to me in an interview.

Question is taken from Comparative Genomics topic in section Collecting & Storing Sequences in Laboratory of Bioinformatics

Answer 1

The incorrect statement about Clusters of Orthologous Groups (COGs) is:

(d) each of the orthologs belongs to a family composed of paralogous sequences but irrelevant or not related to each other.

This statement is incorrect because orthologs are genes in different species that evolved from a common ancestor through speciation. They are similar in sequence and function. Paralogous genes, on the other hand, arise from gene duplication within the same organism and may evolve to have different functions. Therefore, orthologs are not part of families composed of paralogous sequences.