Hox genes are a type of “general purpose gene” that control the selection and placement of certain building elements in complicated organisms. For example, rat’s have a hox gene that controls whether a tail is “built” or not. In the rat’s case, this gene is turned on so there is a tail on the rat. While at first this may seem like useless information, once hox genes are put into an evolutionary perspective they become much more interesting. For example, chickens have a hox gene for teeth, but this gene is turned off. If this gene were to be turned on, and the beak gene were turned off, a chicken could theoretically have teeth. This is possible because the chicken’s DNA still contains the instructions for “building” teeth that its dinosaur ancestors once had. In this sense, hox genes can be helpful in explaining large leaps of evolutionary development, which before seemed impossible to occur so rapidly in such small amounts of time. But why does the hox gene exist? Hox genes are found because they control homologous to other organisms. In other words, many organisms of very different types and ancestries still have the same hox genes. Another example of hox genes in action is allometric growth. Allometric growth is a change in the rate of growth in a certain feature or dimension in comparison to the rest of the body. For example, some of the evolutionary changes responsible for bat wings are due to allometric growth. Since bat wings evolved out of ordinary paws, either the finger bones increased growth rate along with the skin connecting the bones, or the rate of body growth decreased while the paw rate remained constant. Both theories are examples of allometry.
Guest post written by slarsen88