In the ensuing 3.5 billion years, these genes have given rise to the genes that exist today through two major evolutionary mechanisms: duplication and divergence, and exon shuffling.
Exon shuffling is another major evolutionary mechanism.
How did Notch arise by exon shuffling? Choanoflagellates are one-celled eukaryotes that are the closest relatives of animals (Figure 2).
The invention further provides methods for directed ligation of product molecules (i.e., for selective ligation of certain molecules within a collection of molecules), and also for methods of exon shuffling
, in which multiple different product molecules are produced in a single ligation reaction.
I do not discuss the mechanics of gene duplication or exon shuffling
which are the main means by which new molecules arise (Graur and Li, 2000).
The work supports the exon shuffling
theory, which contends that introns act as spacers where breaks for genetic recombination occur.