Retrotransposable elements are major constituents of genomes. These mobile DNA sequences can disrupt genes, induce genomic rearrangements, influence gene expression and mobilize various types of non-autonomous sequences. Their genomic status is still controversial and an object of intense debate in the scientific community. On the one hand, retrotransposable elements are frequently considered as genome parasites or as ‘junk DNA?causing genetic diseases and evolving as retroviruses. On the other hand, mobile DNA and transposition are driving forces of genome evolution. Many regulatory and coding sequences contain parts of transposable elements that are required for proper expression and function of resident genes and proteins. Some mobile sequences have been domesticated by the host and play important cellular roles.

Valuable reading for researchers and teachers involved in genetics, genome structure and evolution, this publication updates the current knowledge on retrotransposition and retrotransposable elements and their impact on gene function and genome evolution.