| Citation | Dr. Southern has done pioneering work on the organization of DNA sequences in chromosomes. Apart from studies on crab poly-AT carried out in the early 1960s, Southern was the first to determine the nucleotide sequence of a eukaryotic chromosomal DNA fraction, demonstrating that a guinea pig 'satellite' had an unexpectantly simple repetitive structure based on a sequence of six nucleotides. In mouse satellite DNA he showed both short and long range periodicities. These and other studies on repetitive DNA he showed both short and long range periodicities. These and other studies on repetitive DNA sequences enabled him to suggest how non-coding chromosomal DNA may have evolved. Southern has devised valuable methods for DNA analysis. His 'blot' technique, for the identification of specific sequences among large populations of fragments generated by endonucleases, has found extremely widespread and important applications. He has also made important observations on the differential transcription of DNA sequences into RNA, and on patterns of DNA methylation. |