Preparation of chromatin containing ribosomal deoxyribonucleic acid from the macronucleus of Tetrahymena pyriformis.

A method is described that enables a chromatin fraction containing ribosomal DNA (DNA containing sequences coding for rRNA) to be prepared from the macronuclei of growing or stationary cultures of Tetrahymena pyriformis. This material is obtained in yields of between 25 and 75% of the theoretical maximum. The DNA in this fraction was identified as ribosomal DNA on the basis of its density and molecular weight, and it appears not to be appreciably contaminated by other DNA. The method relies on the approximate assumption that ribosomal DNA is the smallest species of DNA in chromatin in the nucleus, and avoids the use of mechanical force, or enzyme action, to fractionate chromatin.