A NOVEL MECHANISM GENERATING SHORT DELETION INSERTIONS FOLLOWING SLIPPAGE IS SUGGESTED BY A MUTATION IN THE HUMAN ALPHA(2)-GLOBIN GENE/

A novel mechanism generating short deletion/insertions is described ba sed on a mutation in the human alpha(2)-globin gene, A deletion of 9 b p (codons 39-41) is replaced by an eight nucleotide insertion, duplica ting the adjacent downstream sequence, We propose that the mutation ar ose by slipped strand mispairing (SSM), creating a single-stranded loo p, followed by DNA elongation, strand breathing and the formation of a mismatch bubble, An extensive literature search has revealed six addi tional deletion/insertion mutations in humans in which the inserted nu cleotides come from the same DNA strand. Our model explains all six mu tations, suggesting that rearrangement of a mismatch loop or bubble du ring DNA replication may be not uncommon.