Chromosome breakpoints contribute to genetic variation.

In chapters 6 and 7 of NOT A CHIMP I explain how large structural upheavals in the genome, involving segmental duplication of large sections of DNA, inversions, and deletions, can lead to novel sources of genetic variation because they can either produce a new family of genes, or dupes, upon which natural selection can differentially act, or because they disrupt genes or families of genes when chromosomal breakpoints occur within genes or close by. Now a team led by Harris Lewin, of the University of Illinois, has shown that such chromosome breaks do not occur randomly, invariably occur in gene-rich parts of chromosomes, as opposed to genetic deserts, and in areas abounding in copy number variants of genes, insertions and deletions. Furthermore, different classes of genes are associated with breakage-susceptible to breakage-resistant parts of chromosomes, the former over-represented with genes for immune system and muscle contraction, for instance. Yet more evidence that structural tectonics in the genome are, if anything, more important than prosaic point mutations in the genetic code in providing raw material for natural selection to operate on.