Department of Biological Science

Robert O. Lawton Distinguished Professor Emeritus
Member, National Academy of Sciences of the USA
Ph.D. University of Virginia, 1944

Obituary from American Society of Cell Biology Newsletter, February 1999

Curriculum vitae

Major Research Accomplishments

(1) Demonstrated the labeling with 3H-thymidine of the two DNA subunits of chromosomes and their semiconservative segregation during cell division (1956-57); first evidence for semiconservative replication of DNA. (2) Found the opposite polarity of the two subunits of chromosomes, indicating their analogy to the two chains of the Watson-Crick helix (1958-59). (3) Demonstrated the pattern of labeling of chromosomes over the cell cycle, including the discovery of the late-replicating X chromosome in mammals (1960). (4) Demonstrated that physical exchanges between homologous chromosomes occur during meiosis (1965). (5) Found that replication of DNA in mammalian chromosomes occurs by the production of small segments and later showed that some segments contain ribonucleotides (1969-1973). (6) Isolated and partially characterized the replication complex from mammalian cells in culture (1973-1977). (7) Obtained evidence concerning the kinetics and regulation of initiation in highly synchronized cells at the beginning of S phase. Showed that potential sites are available at 4-micron intervals along the DNA but that, in the normal cycle of cultured fibroblasts, only one in 15-20 of the potential origins is actually used in initiation of DNA replication (1973-1977). (8) (In collaboration with Shinichi Watanabe, graduate student) Cloned many EcoRI segments of Xenopus DNA into an Escherichia coli plasmid and tested these for origins of replication by injecting the supercoiled recombinant plasmids into unfertilized Xenopus eggs. Some sequences function as origins. A 505-base-pair segment containing an origin was sequenced, and experiments were continued to determine the sequences at functional origins (1980-1986). (9) (In collaboration with Karin Sturm and R. Alfred McGraw) Demonstrated by sequencing DNA that there are differences in modification (methylation) of satellite DNA's in cells of various differentiated bovine tissues. Sperm and chorion are methylated at few sites compared to thymus, brain, liver, and kidney cells (1981-1990).

Selected Publications

Taylor, J. H. 1953. Intracellular localization of labeled nucleic acid determined with autoradiographs. Science 118: 555-557.

Taylor, J. H., P. S. Woods, and W. L. Hughes. 1957. The organization and duplication of chromosomes as revealed by autoradiographic studies using tritium-labeled thymidine. Proc. Natl. Acad. Sci. USA 43: 122-128.

Taylor, J. H. 1989. DNA synthesis in chromosomes: implications of early experiments. BioEssays 10: 121-124.

Taylor, J. H. 1990. Chromosome reproduction: units of DNA segregation. BioEssays 12: 289-296.

Taylor, J. H. 1991. My favorite cells with large chromosomes. BioEssays 13: 479-487.

Taylor, J. H. 1991. Tritium-labeled thymidine and early insights into DNA replication and chromosome structure. Trends in Biochemical Sciences 19: 479-487.