Daily Archives: March 1, 2010

Deepening the Clues

I have already provided a couple of clues that suggest introns played some important role in the emergence of multicellular life.  Let me now add a little depth to those clues.

We saw that the general rule was that complex multicellular genomes tend to be intron-rich, while the genomes of single-celled organisms tend to have very few introns.

But there is a glaring exception.  Recall the choanoflagellates – the single-celled organisms thought to be most closely related to metazoans.  When their genome was sequenced, it provided a big boost to the hypothesis of front-loading, as it contained a whole toolkit of genes needed for metazoan existence, including the information to make cell adhesion domains, extracellular-matrix-associated protein domains, and an elaborate phosphotyrosine signalling machinery (all of these once believed to be specific to metazoans).

So do the choanoflagellates have introns?

Oh yeah.

Continue reading