APBI 200 Lecture : Biol 121- 2010.03.29- Evolution- Great Changes, Diversity and Divergence (Ch. 27, 34).docx
Document Summary
Evo-devo: gene duplications and the cambrian explosion. Hox genes are important in specifying morphological traits and in development (order and place) and are responsible for the 3d pattern of structures. Increased complexity of hox complex is related to the increased complexity of organisms. There are groups that branch off early (like jellyfish) that have fewer hox genes and simpler body plans. Conversely, groups that do not branch off early have more hox genes and more complex body plans. Also genes within a cluster are very similar which is perhaps due to duplication. The whole hox cluster could have been duplicated twice to lead to vertebrates. Exception: crustaceans are complex but have only 5 hox genes. When gene duplication occurred, new hox genes were greated, b/c genes within the cluster are similar in structure and base sequence. The entire hox cluster was duplicated, and then duplicated again, in the lineage leading to vertebrates.
