Large-Scale Gene and Ancient Genome Duplications

Duplications of genetic elements can occur by a variety of mechanisms and at different chromosomal and temporal scales. This chapter deals with an impor-tant subset of these, namely large-scale gene duplications (versus the small-scale evens discussed in Chapter 5) and ancient duplications of whole genomes (versus more recent pollploidy in plants and animals, dealt with in Chapters 7 and 8, respectively). The emphasis in this case is on the techniques used to identify, date, and otherwise investigate such events, as illustrated by some key recent o<amples. As will be shown, analyses of di{ferent eukaryotes clearly indicate that significant portions of their genomes consist of duplicated gene loci, and that many of these gene duplicates have been formed by the duplicarion of chromosomal blocks and/or entire genomes. The timings of these events, in some cases dating back hundreds of millions of years, suggest that they have played an important role in influencing major pattems of evolutionary diversification. The Elotutior of the G.w, edited by TR Gregor