According to Professor James A. Yorke, each individual today is the result of approximately 1014 genetic "experiments," but today's bacterial cells are the result of 1034 "experiments."
This simple mathematical exercise implies that bacteria are about 1020 times more genetically complex than we are.
Yorke, a University Professor of Mathematics and Physics at the University of Maryland-College Park, spoke on genetic complexity in his lecture entitled "Determining the DNA Sequence: A Billion Dollar Logic Puzzle."
This was the third and final lecture in a series of lectures that the math department hosts every year in honor of alumnus Norbert Wiener (A' 09).
Yorke and Mathematics Professor Boris Hasselblatt both work in a field known as dynamical systems, which includes chaos theory, a term which Yorke coined.
"Chaos concerns situations where a very small change results in a big change and there are lots of such events," Yorke said in an interview with the Daily. "You could imagine that when you were conceived, with a very small change, you could have been [the opposite sex]."
Although Yorke's first lecture was on chaos, his other talks focused more on topics in medicine and biology.
His second lecture concerned AIDS and when HIV-infected patients are most contagious. The study he worked on, which was published in the Journal of AIDS/HIV in 2005, found that "people who are in the later symptomatic stage are highly infectious."
This is particularly important because a month ago, the United States changed its HIV screening policy to make HIV testing more widely available, Yorke said.
Last night, he focused on the process involved in sequencing a genome.
"Genome sequencing is by no means a solved problem," he said. "It's like a one-dimensional jigsaw puzzle."
Sequencing involves matching the fronts and backs of different fragments of DNA, based on whether they contain the same order of basic elements.
Although this may seem easy, errors in copying and reading the bases make sequencing much more difficult, he said.
Copying errors, also known as mutations, come in three varieties, Yorke said. Segmental duplication and segmental deletion are the copying or deletion of a strand of bases, while point mutations only change one base.
According to Yorke, segmental duplications are the least harmful to the evolutionary process, since they don't potentially erase or change an essential gene.
"Trying to understand segmental duplication and segmental deletion is central to my studies," he added.
All sequence data determined by the lab at College Park and other labs is available in the massive archive of all such data on the National Center for Biotechnology Information Web site, and the genomes sequenced include the human, mouse, rat, chimpanzee, as well as the zebra fish genome.
According to Yorke, the United States will spend in excess of $1 billion dollars in the next few years on DNA sequencing.
