I am currently reading from Chapter 15 in Principles of Life, 2nd Edition:

Many gene duplications affect only one or a few genes at a time, but in some cases entire genomes may be duplicated. When all the genes are duplicated, there are massive opportunities for new functions to evolve. That is exactly what seems to have happened during the course of vertebrate evolution. The genomes of the jawed vertebrates have four diploid sets of many major genes, which leads biologists to conclude that two genome-wide duplication events occurred in the ancestor of these species. These duplications allowed considerable specialization of individual vertebrate genes, many of which are now highly tissue-specific in their expression.

My question is: how exactly does duplicating a genome enable specialization of genes? In other words, after vertebrates underwent genome duplication, how did one copy of the genome become "highly tissue-specific"?


1 Answer 1


With a single copy gene, mutations may affect some vital function and are therefore often deleterious and negatively selected. Immediately after a duplication event, there is a level of redundancy in gene function and mutations in one copy giving rise to novel phenotypes are more easily tolerated since the ancestral function is retained by the paralogous gene.

Some reading material, if you feel so inclined:


Functional Divergence

Functional divergence is the process by which genes, after gene duplication, shift in function from an ancestral function. Functional divergence can result in either subfunctionalization, where a paralog specializes one of several ancestral functions, or neofunctionalization, where a totally new functional capability evolves.


Following the gene duplication event there are two identical copies of the ancestral gene performing exactly the same function. This redundancy allows one the copies to take on a new function.


Specialization is a unique model of subfunctionalization, in which paralogs divide into various areas of specialty rather than function. In this model both gene copies perform exactly the same ancestral function. For instance, while the ancestral gene may have performed its function in all tissues, developmental stage, and environmental conditions, the paralogous genes become specialists, dividing themselves among different tissues, developmental stages, and environmental conditions.

Kryuchkova-Mostacci N, Robinson-Rechavi M. 2016. Tissue-Specificity of Gene Expression Diverges Slowly between Orthologs, and Rapidly between Paralogs. PLoS Comput Biol 12:e1005274.

The most widely accepted model is that orthologs diverge slower, and that the generation of paralogs through duplication leads to strong divergence and even change of function.

Soria PS, McGary KL, Rokas A. 2014. Functional divergence for every paralog. Mol Biol Evol 31:984-992.

Because genes can be constrained by selection at more than one phenotypic level, the relaxation of constraints following gene duplication allows for functional divergence (FD) along multiple phenotypic axes.


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