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. Author manuscript; available in PMC: 2006 May 23.
Published in final edited form as: Annu Rev Genet. 2005;39:121–152. doi: 10.1146/annurev.genet.39.073003.112240

Figure 6.

Figure 6

Evolutionary changes of functional OR genes. (a) The most recent common ancestor (MRCA) between humans and mice had approximately 754 functional OR genes. The number of functional OR genes increased to 1037 in the mouse lineage, whereas it declined to 388 in the human lineage. (b) The MRCA between jawed and jawless fishes had at least two functional genes, whereas the MRCA between fishes and tetrapods had at least 9 functional OR genes. Class II genes (blue circle) expanded enormously in amphibians and mammals.