It’s All in The Genes

Fact: Tomatoes have more genes than humans.

We think of humans as the most complex and advanced of all living thing on this planet – so naturally you might think that we require the most genetic material to make such a complicated animal. How wrong you would be.

Your average human genome contains ~21,000 genes, while your average tomato comes in at ~31,000 genes. That means tomatoes are actually about 50% more ‘complex’ at a genetic level than humans. So why are they not farming us for their food?

The key here is that the amount of DNA or the number of genes in an organism actually has very little to do with how complex that organism is. In fact, the largest known genome – featuring 40 chromosomes and clocking in at 150 billion base pairs – belongs to the relatively normal plant Paris japonica, and not to some really complicated freak of nature.

One reason for the variation in genome sizes is that massive genomes (such as that of Paris japonica) often contain much more ‘junk DNA’ – DNA which does not code for the production of a protien – rather than more genes. In fact, even when there are a larger number of genes they may not be useful in the traditional sense: the tomato, for example, has eight copies of each gene rather than the two copies that we see in humans, and so many of these genes are completely redundant.

Why have so many copies of a single gene? The theory is that the origional gene can perform its important function while the copied gene can change (or mutate) into a new gene that might do something useful, thus allowing the organism to evolve.

Sonext time you pick a tomato, show some respect.

Another one of Mr Shaunak’s Little Bites of Science’
Image under Creative Commons license

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