Mouse major (gamma) satellite DNA is highly conserved and organized into extremely long tandem arrays: implications for recombination between nonhomologous chromosomes.

We have isolated and sequenced 30 independent clones derived from MnlI digestion of purified mouse major (gamma) satellite DNA. These clones contained between 0.9 and 1.1 gamma monomeric units derived presumably from random chromosomal sources. Individual clones showed a mean deviation from the mouse consensus satellite sequence of 3.9%, with a range of 0.9-9.1%. Cleavage of total mouse LTK cell genomic DNA with three different restriction enzymes (HindIII, BglII, BamHI) that do not cut within satellite monomers, followed by Southern and pulsed-field gel electrophoretic analyses, showed that the majority of monomers were organized into largely uninterrupted arrays that varied from a minimum of 240 kb to greater than 2000 kb in length. We suggest that the high degree of conservation of the mouse gamma-satellite sequences throughout the mouse genome results from frequent recombinational exchange between nonhomologous chromosomes. Further, this same process, facilitated by the all-acrocentric constitution of the typical mouse karyotype, and the extremely long and homologous gamma-satellite arrays, may be related to the common occurrence of Robertsonian translocation in mouse.