BIOLOGY 1M03 Lecture 14: Chapter 27, HHE Chapter 9, Lecture 14
4 Feb 2018
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Document Summary
Events in the phanerzoic eon (palaeozoic, mesozoic, and cenozoic eras) Evolutionary development; modularity, switches and gradients, genes and complexity, gene and genome duplication. Hox gene evolution: gene and genome duplication. Some researchers predicted a strong association between the order in which animal lineages appeared during evolutionary history, the number of hox genes present in each lineage, and each lineage"s morphological complexity and body size. Before we had the complete genome sequences of species, people thought that gene number was positively correlated with morphological complexity. The logic behind this new genes, new bodies hypothesis was that existing homeotic genes could have been duplicated before and during the ce, producing new body plans and appendages. There is evidence to show that hox genes were duplicated several times that could contribute to new body parts and appendages. Some species (sponges and jellyfish) have homologs of hox genes but they are not located on the same chromosome and do not have colinearity.
