Non-neutral processes drive the nucleotide composition of non-coding sequences in Drosophila

Haddrill, Penelope R and Charlesworth, Brian (2008) Non-neutral processes drive the nucleotide composition of non-coding sequences in Drosophila. Biology Letters, 4 (4). pp. 438-441. ISSN 1744-9561

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Abstract

The nature of the forces affecting base composition is a key question in genome evolution. There is uncertainty as to whether differences in the GC contents of non-coding sequences reflect differences in mutational bias, or in the intensity of selection or biased gene conversion. We have used a polymorphism dataset for non-coding sequences on the X chromosome of Drosophila simulans to examine this question. The proportion of GC-->AT versus AT-->GC polymorphic mutations in a locus is correlated with its GC content. This implies the action of forces that favour GC over AT base pairs, which are apparently strongest in GC-rich sequences.