Non-LTR retrotransposons (such as the human L1 elements) are sometimes falsely referred to as retroposons. Retroposition accounts for approximately 10,000 gene-duplication events in the human genome, of which approximately 10% are functional. Such genes are called retrogenes and represent a certain type of retroposons. A classical event is the retroposition of a spliced pre-mRNA molecule of the c-scr gene into the proviral ancestor of the Rous Sarcoma Virus (RSV). The retroposed c-src pre-mRNA still contained a single intron and within RSV is now referred to as v-src gene.
Emerson JJ, Kaessmann H, Betran E, Long M (2004) Extensive gene traffic on the mammalian X chromosome. Science 303:537-540