During the past year detailed studies on DNA gyrase have continued resulting in further specification on the mechanism of DNA binding and cutting, the development of in vitro system for the study of N4 replication and preparation of recombinant plasmids containing bacteriophage lambda stick ends (cosmids). Yeast mutants particularly useful for the study of recombination have been isolated and studied and a mechanism for the non-reciprocal transfer of information from one portion of a chromosome to another portion of the same chromosome has been discovered. Proteins binding to 5 and 5.8 S ribosomal RNA and initiator and elongator tRNA's have been identified. Differences between the site of inhibition of different DNA polymerase acting on carcinogen-reacted DNA templates have been observed.