Nucleotide sequence repetition: a rapidly reassociating fraction of mouse DNA.

The separated complemnentary strands of a minor component in mouse DNA reassociate with each other much more rapidly than do the complementary strands of other DNA's including those of the principal part of mouse DNA. This difference in capacity of the strands to reassociate can be used to effect a preparative separation of the minor component from the principal fraction. The rate constant for reassociation of the minor component, compared with those of viral and bacterial DNA's, indicates that the minor component consists of a short nucleotide sequence present in about one million copies.