Evolutionary forces generating sequence homogeneity and heterogeneity within retrotransposon families

Genome projects allow us to sample copies of a retrotransposon sequence family residing in a host genome. The variation in DNA sequence between these individual copies will reflect the evolutionary process that has spread the sequences through the genome. Here I review quantitatively the expected diversity of elements belonging to a transposable genetic element family. I use a simple neutral model for replicative mobile DNAs such as retrotransposons to predict the extent of sequence variability between members of a single family of transposable elements, both within and between species. The effects of horizontal transfer are also explored. I also consider the impact on these distributions of an increase in transposition rate arising from a mutational change in copy of the sequence. In addition, I consider the question of the interaction between retrotransposons and their hosts, and the causes of the abundance of transposable elements in the genomes that they occupy. Copyright (c) 2005 S. KargerAG, Basel.