In with the Old, in with the New: The Promiscuity of the Duplication Process Engenders Diverse Pathways for Novel Gene Creation
Figure 3
The creation of two classes of retrocopies via RNA-mediated duplication events. (a) Processed copies are created when a spliced mRNA of an ancestral locus is reverse transcribed into cDNA, leading to the creation of a single-exon duplicate from a multiexonic ancestral gene. The processed copy lacks all ancestral introns and the ancestral promoter, while possessing a poly(A) tail at the 3′ end and flanking direct repeats at both the 5′ and 3′ end. (b) A semiprocessed copy can be formed via retrotransposition of a partially-processed pre-mRNA transcript leading to the inheritance of some ancestral introns and flanking region sequence. In the schematic, the retrocopy possesses a poly(A) tail and direct flanking repeats. It lacks introns 2 and 3 but has inherited the ancestral intron 1 and a portion of the ancestral promoter.
