Interspersion of repetitive and single-copy sequences in nuclear ribonucleic acid of high molecular weight.

Nuclear RNA of high molecular weight, approximately 15 to 30 x 10(3) nucleotides long, isolated from rat ascites cells, has been shown previously to contain both middle repetitive and single-copy sequences. However, it was not known whether these sequences were located on separate molecules or whether they were interspersed within the same molecule. The present communication distinguishes between these possibilities and shows that a large proportion of nuclear RNA of high molecular weight consists of interspersed middle repetitive and single-copy sequences.