Segmental duplications and the evolution of the primate genome

Abstract

Initial human genome sequence analysis has revealed large segments of nearly identical sequence in particular chromosomal regions. The recent origin of these segments and their abundance (approximately 5%) has challenged investigators to elucidate their underlying mechanism and role in primate genome evolution. Although the precise fraction is unknown, some of these duplicated segments have recently been shown to be associated with rapid gene innovation and chromosomal rearrangement in the genomes of man and the great apes.

Interchromosomal segmental duplications of the pericentromeric region on the human Y chromosome

“…These larger segments consist of numerous smaller duplication modules of diverse evolutionary origin. Taken together, these findings fit with the proposed two-step model of pericentromeric duplication wherein an initial process of transposition seeding (accumulation of smaller duplications within pericentromeric regions) is followed by pericentromeric exchange (spreading of larger patchwork blocks to pericentromeric regions of nonhomologous chromosomes) (Eichler et al 1997;Horvath et al 2000b;Luijten et al 2000;Samonte and Eichler 2002). In contrast, the most pericentromeric position in the euchromatic island is exclusively present on chromosome 11.…”

“…Such highly duplicated regions with a locally increased number of recombinationpromoting CAGGG repeats are prone to chromosomal rearrangements (Ji et al 2000;Samonte and Eichler 2002;Stankiewicz and Lupski 2002). These rearrangements might lead to an abnormal phenotype by disruption or dosage alteration of the involved genes.…”

“…Analysis of these regions has also revealed that they are composed of DNA containing partial copies or complete genic sequences composed of exons and introns. Indeed, these highly active regions have also been demonstrated to be the birthplace of novel genes (Samonte and Eichler 2002). We have isolated and sequenced a 554-kb genomic segment from the human Y chromosome that contains a 450-kb euchromatic island hidden between satellite 3 sequence, adjacent to the centromere on the long arm of the chromosome.…”

No evidence for maintenance of a sympatricHeliconiusspecies barrier by chromosomal inversions

“…This contrasts with, for example, the many fixed or polymorphic inversions in the genomes of Drosophila (Krimbas and Powell 1992), Anopheles (Ayala et al. 2014), and primates (Samonte and Eichler 2002), and especially with the solid case for the influence of inversions on speciation between sympatric populations of D. pseudoobscura and D. persimilis (Noor et al. 2001; Machado et al.…”

Nouvelles données en génétique chromosomique

“…La structure des duplicons peut être assez simple ou complexe, composée de différents modules dupliqués/transposés à partir de chromosomes différents, puis à nouveau dupliqués et remaniés [9] (Figure 1). Par hybridation in situ sur différents génomes et comparaison de séquences, il a été montré que ces blocs se sont formés par transposition duplicative tout au long de l'évolution des primates, c'est-à-dire au cours des dernières 40 millions d'années [10].…”