Chapter Three: Handy Genes

This chapter was all about genes and how we can study DNA to catalogue genetic differences by finding genetic switches that may have changed during the origin of limbs....almost like cataloguing evolution. Shubin revealed to us that embryos are very important for DNA study. By studying chicken eggs, we discovered the ZPA gene (zone of polarizing activity). This gene controls how digits form and what they look like. Once this gene was discovered, there was experiments that involved flies, which allowed us to discover the hedgehog. My first thought was why would someone call a gene a hedgehog? It seemed weird to me. But then it explained that it reminded the scientists of the bristles of a hedgehog. From here we discovered the sonic hedgehog (like the videogame! Haha) that acts the same way as the ZPA in chickens. When I found out that every animal has a sonic hedgehog, I was stunned. Like the experiments with sharks and skates proved a sonic hedgehog gene that reacted the same way as the genes found in chickens and other animals. The cool part was that I found out that all appendages are built by similar kinds of genes. Which means, evolution did not involve the origin of new DNA, but involved ancient genes in new ways to make limbs, fingers, and toes. How cool is that? The same genes used to make different things in nature! This shows that connections among living creatures truly runs deep....DNA deep!