Since paralogs increase the size of the genome and provide more opportunity for the evolution of novel characteristics, would they be more prone to selection?


1 Answer 1


Exactly . Paralogs and orthologs , both go under natural selection. But harmful mutations tend to have a less fatal effect if they happen to paralogs as there would be a backup for the malfunctioning protein. In paralogs, if a bad mutation happens to a protein, the paralogous protein will compensate and help the organism maintain its function but in orthologs one mistake is enough to do harm because there are no other proteins to perform the function of the wild protein.

All the different members of the tubulin family of genes (and proteins) are sufficiently similar in sequence to suggest a common ancestral sequence. Thus all these sequences are considered to be homologous. More specifically, sequences that presumably diverged as a result of gene duplication (e.g., the α- and β-tubulin sequences) are described as paralogous. Sequences that arose because of speciation (e.g., the α-tubulin genes in different species) are described as orthologous

Reference : Molecular Cell Biology of Lodish et al 8th edition page 325

Also see Campbell Biology 9th edition chapter 26 section 26-4

  • $\begingroup$ this is a good answer, but it would be helpful to include a source or citation. $\endgroup$ Nov 12, 2020 at 21:29
  • $\begingroup$ @sam, thanks for the great answer! I am just wondering though how the impact of selection would differ in protein coding regions.... I know it would be more impactful in this region as opposed to non coding, but im not sure how the impact differs between protein coding regions.. or why? thanks! $\endgroup$ Nov 13, 2020 at 13:57
  • $\begingroup$ @Manon Valiquette , natural selection effects the whole gene. (Beneficial) selection in protein coding regions includes 1.Active sites / binding sites for complexes 2.Allosteric domains 3.Structural/Less important sections. In 1 , any change leads to a large scale of "FUNCTION" and the "AFFINITY" to ligand of the protein/enzyme. In 2 alternation of sequence leads to changes in "AFFINITY" for the ligand and more importantly "RATE OF CATALYSIS", while changes in 3 tend to have a less impact on the protein. Plus selection can also occur in non coding regions which mainly result in --- $\endgroup$ Nov 13, 2020 at 17:47
  • $\begingroup$ --- "Gene expressing patterns and timing and amount of transcription" . for example a selection in promoter sequence can increase the rate of trancription of a specific gene , leading to overexpression of it which sometimes may be beneficial. I hope that I've understood your question correctly. $\endgroup$ Nov 13, 2020 at 17:50

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