What are Hox genes and why are they so important, in Your Inner Fish?Chapter 5 - Getting Ahead

In Your Inner Fish: A Journey into
the 3.5 Billion Year History of the Human Body, Neil Shubin
writes about the importance of Hox genes in his research. Hox genes are like an
instruction sheet for an embryo. They help organize the basic body layout of many
organisms. In an effort to find genetic evolutionary evidence of human beings'
ancestors, Shubin and his cohorts discovered that the genetic capability to build limbs
was actually present in primitive fish. Shubin looked at Hox genes in paddlefish by
inserting molecular markers and was able to show the same activity was present in
tetrapod limbs. Tetrapods have a second stage of Hox gene expression where hands and
feet form. This is significant because it links fish and tetrapods in the
line of evolution as common ancestors.