Robertsonian chromosome recombinants are rare in cancer

Whole-arm Robertsonian rearrangements are common constitutional changes of chromosomes that possess unusual properties. They occur spontaneously, are not inducible by ionizing radiation or clastogenic chemicals, show an exceptionally high meiotic mutation rate and nonrandom chromosome composition. A sample of 30 Robertsonian rearrangements in cancer patients revealed only three to have been acquired, none as a primary or significant secondary cancer chromosome change. The frequency of Robertsonian rearrangements is in the range of one per 1,100 at birth versus one acquired per 10,000 in cancer. Consistent with the prediction that Robertsonian rearrangements are recombinants, a subfamily of alpha satellite DNA displays selective homology between the centromeric regions of acrocentric autosomes proportional to their preferential entry into Robertsonian chromosomes. Recombination leading to Robertsonian rearrangements is common in meiosis, but is rare in mitosis. Hence, Robertsonian rearrangements are rare in cancer.