Model of unequal chromosomal crossing over in DNA sequences11This work is supported by NIH-HGP.

It is known that some dimeric tandem repeats (DTR) are very abundant in noncoding DNA. We find that certain DTR length distribution functions in noncoding DNA can be fit by a power law function. We analyze a simplified model of unequal chromosomal crossing over and find that it produces a stable power law length distribution function, with the exponent μ=2. Although the exponent predicted by this model differs from those observed in nature, we argue that the biophysical process underlying this model provides the major contribution to the DTR length distribution function.