Answer to Question #184006 in Evolution for Madison Brennan

Question

What is the MOST likely reason that many homeotic gene sequences are very, very similar even in species that do not share a recent common ancestor?

Answer 1

Homeotic genes are genes that control development of whole body sequents or structures. Such genes are homologous across the animal kingdom, that is their genetic sequence and position on chromosomes are similar across most animals because of their presence in a common ancestor. Although there seems to be a no recent common ancestor for the organisms that bera these genes, there is still an earlier common ancestor for all the organisms. A good example is all organisms having a bilateral symmetry; they may look so diverse that one cannot imagine a common ancestor for all of them. However, these genes must have evolved earlier in the animal evolution from a single gene by duplication and subsequent divergence. Thus, such genes must have been present in a common ancestor of all bilaterally symmetrical animals.