Problem: About 40% of the human genome is made up of retrotransposon DNA. Describe the two major classes of retrotransposon DNA and for each class, describe the mechanism of retrotransposition. Not just germline retrotransposition can occur, but it is estimated that at least 6 out of 10 brain cells have a novel retrotransposition event that occurred during brain development. Describe the typical chromosomal location and functional consequences of such somatic retrotransposition events.