Roy John Britten | Biography

Roy J. Britten discovered repeated DNA sequences in higher organisms' genomes. Britten conducted research on repetitive DNA and its origins which provided a foundation for advanced genetic investigations regarding human evolution. Britten's molecular evolution research benefited from the work of cytogeneticist Barbara McClintock (1902-1992). She hypothesized in the 1940s that DNA sequences were not always static because some genetic elements moved on or between chromosomes resulting in physical variations in organisms, due to the presence or absence of genes. Although McClintock's jumping gene theory was not immediately understood, molecular biologists gradually identified these mobile elements as transposons and began to study their role in evolution. Britten was one of the first researchers to detect transposons in mammal genomes.

Born in Washington, D.C., Britten became enthusiastic about science as a child. His physics studies at the University of Virginia were interrupted when he was invited to work on the Manhattan Project. Receiving a doctorate in nuclear physics from Princeton University, Britten concentrated his post-doctoral research in biophysics instead. At Cold Spring Harbor, he focused on phages, then examined DNA hybridization kinetics with researchers in the Department of Terrestrial Magnetism of the Carnegie Institution. In 1968, Britten, with colleague David Kohne, proved that eukaryotic genomes consist of numerous repetitive, non-coding DNA sequences. They had heated DNA samples to separate the double strands, then measured the rate for the strands to reassociate, realizing that the number of varying sequences influenced the reassociation rate.

Britten applied evolutionary biology techniques to repetitive DNA in an attempt to determine its origin. He demonstrated how DNA variation was the basis of evolution. Britten theorized about the role of systems that regulate genetic activity and how changes to those systems or to genes affect evolution. He examined the source of genomic change, such as amino acids being replaced in proteins. Britten studied the role of mobile elements, specifically DNA sequences, that alter how genes behave and hypothesized that these transposons were crucial for variation.

Britten focused on the concept of how these mobile elements might influence evolution. He stressed that transposons modify gene expression patterns and have a greater effect on organisms than mutations. Britten emphasized that transposons provide the power needed to achieve evolution. He explored the effect of the transposon known as the Alu element on gene expression. These transposons are found only in primates and are the most numerous transposon in human genomes, comprising five to ten percent of human DNA which has 500,000 to 1,000,000 copies of the Alu sequence. The Alu sequence is the most frequent form of what geneticists refer to as junk DNA, because its function in the strand is not obvious. Britten's colleagues considered him the father of junk DNA research, as Britten stressed that such repetitive sequences in DNA strands merited research, and may eventually prove useful.

Britten developed a DNA hybridization technique to analyze genome composition and measure the genetic differences between organisms. When denaturing, or breaking the bonds holding DNA strands together by boiling the solution, Britten introduced DNA from other species so that strands of the original DNA sample was forced to bond with strands of the new DNA when the solution cooled. The result is a hybrid DNA, or heteroduplex, consisting of labeled DNA known as the tracer and the second species' DNA known as the driver. Because fewer hydrogen bonds are present in the hybrid DNA, it is denatured at lower temperatures. Analysis of the process to produce a homoduplex provides information about each species' genome.

Associated with the California Institute of Technology since 1970, Britten is an investigator for the gene regulation research group and is also an adjunct professor of Genome Organization and Evolution at the University of California, Irvine. In the 1980s Yale DNA hybridization conundrum, Britten supported the DNA hybridization findings of Charles Sibley and Jon Ahlquist regarding the genetic differences of humans, chimpanzees, and gorillas. They had used Britten's molecular technique to analyze the genomic composition of each species and concluded that chimpanzees were more closely related to humans than they were gorillas. Many geneticists who were unfamiliar with using molecular methods for taxonomy attacked the data as questionable and said the results were flawed. Having seen their data, Britten validated Sibley's and Ahlquist's findings.

Molecular biologists have benefited from Britten's research because they have become aware that transposons are essential to how organisms function and they potentially have a significant evolutionary role.