Cell 138, 855–869 (2009)

Theory predicts the chipping away of the male Y chromosome owing to the fact that, for the most part, it has no recombination partner during meiosis, the sexual form of cell division. But male-specific genes on the Y persist, protected in part by palindromic DNA repeats that are maintained through recombination events between each other. These repeats, say David Page of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, and his collaborators, can also be Y's Achilles' heel.

The researchers propose a mechanism by which a crossover event after chromosomal replication links the two copies of the chromosome together at a palindrome, creating a larger, abnormal chromosome. These 'isodicentric' Y chromosomes are implicated in sex reversal, Turner's syndrome and male infertility. In a study of samples from 2,380 patients with suspected Y-chromosome defects, the authors identified 51 that apparently formed by this mechanism.