I’ve been intrigued by gene duplication and want to learn more about it.

I’ve read the following from here:

several studies suggest that the proportion of duplicated genes retained in vertebrate genomes is much higher than is predicted by this model [4-6]. This has led to the suggestion of an alternative model whereby complementary degenerative mutations in independent subfunctions of each gene copy permits their preservation in the genome, as both copies of the gene are now required to recapitulate the full range of functions present in the single ancestral gene. This was formalized in the Duplication-Degeneration-Complementation (DDC) model [7] in a process referred to as subfunctionalization.

Can someone explain this? What is meant by “both copies of the gene are now required to recapitulate the full range of functions present in the single ancestral gene”?

Can you suggest any other good articles on gene duplication?

  • $\begingroup$ I would interpret that to be a situation where a gene codes for an enzyme that does some necessary metabolic reaction that needs 2 steps, A -> B -> C. The gene gets duplicated, but in order to preserve both copies each copy needs to mutate. Let's say copy 1 can only do A -> B now, and copy 2 can only do B -> C. This means you need both copies to do A -> B -> C. Alternatively, copy 1 could still do A -> B -> C and copy 2 picks up a gain of function mutation that allows A -> B -> D or something. As long as D increases the odds of reproductive success the second gene copy is selected for. $\endgroup$
    – user137
    Commented Oct 15, 2014 at 15:26

1 Answer 1


Suppose a gene performs two distinct functions 1 and 2, both of which are essential. We'll call this gene A, for ancestral gene.

A duplication copies A to another locus. Now there are two genes, A and B, that perform the same two functions. At this point, if either A or B is deleted, the organism is fine.

Over evolutionary time, A and B undergo genetic drift to become A' and B', respectively. Let's say that B' loses function 1, and that A' loses function 2. This isn't a problem for the organism since A' still performs function 1, and B' still performs function 2. In other words, the two genes complement each other.

However, now A' can't be deleted without losing function 1, and, similarly, B' can't be deleted without losing function 2. The result is that both genes are fixed in the genome by evolution.

This means that now, after hundreds of millions of years of relevant evolution and genetic drift, we many duplications like A' and B'. The key to this is that through genetic drift with no selective pressure, it's very easy to lose function but extremely difficult to gain it.

As for your second question, I'll look for a paper on gene duplications that I think would be the most helpful, but there are many.


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