Using CRISPR to Define the Different Regions of Fish Fins

Scientists used CRISPR to test whether genes that sculpt regions of fish fins are present in humans and mice. When they knocked out the genes that form a mouse limb, it turned out we were missing terminal end of their fin. It really came down to another subset of genes that didn't define the region, but made new kinds of bones in the region. So it's a long way of saying that the basic architecture of fins and limbs have a shared genetic activity despite the fact that the fish and the mice have been separate evolutionarily for almost 400 million years.