Molecular parasites, such as transposable elements, are segments of DNA that integrate into chromosomes and proliferate to become highly repetitive within the genome. This proliferation is often harmful to the genome and creates strong selection pressure to counter their activity. In the fungus Microbotryum violaceum a genomic defense mechanism ("repeat-induced point mutations") acts to change the DNA sequence of molecular parasites thus destroying their ability to proliferate. Empirical and theoretical studies will investigate the evolution of molecular parasites as they appear to engage in an arms race with the host genome in order to elude its defensive mechanisms.
Molecular parasites are highly influential components of the genomes of nearly all organisms, with effects upon such fundamental traits as genome size, mutation rates, DNA structure, and mating systems. The activity of molecular parasites has also been implicated in many human-inherited diseases and chromosome rearrangements. Therefore, investigation into which factors limit the evolution of molecular parasites will advance our understanding of genome structure and of particular threats to genetic stability. This research also has broad theoretical implications because it addresses the unique nature of DNA-based parasitism that allows for co-evolution between the molecular parasites and the genomes they inhabit.
