Natural gene duplication plays a major role in evolution. It is also implicated in several forms of human cancer including primary mediastinal B cell lymphoma and Hodgkin's lymphoma. In this context the term "amplicon" can refer both to a section of chromosomal DNA that has been excised, amplified, and reinserted elsewhere in the genome, and to a fragment of extrachromasomal DNA known as a double minute, each of which can be composed of one or more genes. Amplification of the genes encoded by these amplicons generally increases transcription of those genes and ultimately the volume of associated proteins.