UC Davis experts: Experts on basic DNA research

The year 2003 marked the 50th anniversary of one of the most important discoveries of modern science, the double helix structure of DNA. Since 1953, DNA research has had an impact on everything from biology, agriculture and medicine to criminal law and justice, art and politics. At UC Davis, one of the nation's leading research universities in biological sciences, a wide range of experts are available to discuss the significance of Watson and Crick's discovery; current research in DNA; and what the future may hold.

• DNA structure: more than a double helix
• DNA repair
• 'Junk' DNA
• Genetics and evolution of bacteria
• Molecular clocks and the tree of life
• Genes, development and evolution
• Population genetics and DNA

DNA structure: more than a double helix

The famous double helix is actually supported by many different proteins that allow it to be read, copied and repaired. Working out what those proteins are and how they work together is the aim of the Center for Genetics and Development at UC Davis, led by Stephen Kowalczykowski, professor of microbiology and molecular cell biology. Kowalczykowski's own laboratory studies the family of proteins that allow DNA strands to cross over and recombine, creating genetic variation. They recently developed techniques to view, in real time, a single molecule of a protein called helicase unwinding a DNA strand -- a crucial step in DNA replication. Other researchers affiliated with the center study how DNA is packaged into chromosomes and how chromosomes separate, move and find each other again when cells divide. Contacts: Stephen Kowalczykowski, Center for Genetics and Development, (530) 752-5938, sckowalczykowski@ucdavis.edu.

DNA repair

When DNA is copied, or damaged by chemicals or radiation, errors can creep in -- 'typos' in the genetic code. Those errors can lead to genetic defects or diseases such as cancer, so all living cells have proteins that can check and repair DNA. UC Davis researchers Anne Britt, Ken Burtis and Wolf-Dietrich Heyer study DNA repair in plants, fruit flies and yeast, respectively. The genes involved turn out to be very similar, despite hundreds of millions of years of separate evolution. For example, when Britt collaborated on sequencing the first plant genome, Arabidopsis thaliana, she found that of 27 plant genes closely related to genes for human diseases, one-third were for DNA repair genes. Human forms of those genes were linked to some forms of cancer and the hereditary disease Xeroderma pigmentosa.

Contacts: Anne Britt, Plant Biology, (530) 752-0699, abbritt@ucdavis.edu; Ken Burtis, Molecular and Cellular Biology, (530) 752-4188, kcburtis@ucdavis.edu; Wolf-Dietrich Heyer, Microbiology, (530) 752-3001, wdheyer@ucdavis.edu.

'Junk' DNA

Genome sequencing shows that actual genes make up only a small part of the DNA in most animals and plants. Much of the rest consists of repeated sequences and other so-called 'junk' DNA with no obvious function. Carl Schmid, a professor of chemistry and molecular cell biology at UC Davis, discovered one of these repeat sequences, the Alu repeat, in the mid-1970s. There are about a million copies of the Alu repeat scattered throughout the human genome, making up almost 10 percent of the total. Alu repeats can also move around the genome, sometimes inserting into genes and disrupting their function -- a phenomenon first shown in insects by UC Davis professor emeritus Melvin Green. Schmid's research has shown that Alu repeats respond to environmental stresses such as heat, leading to the proposal that they are not junk at all but regulate other genes. They may also affect the structure and shape of DNA molecules and chromosomes. Contact: Carl Schmid, Chemistry, (530) 752-3003, cwschmid@ucdavis.edu.

Genetics and evolution of bacteria

John Roth, professor of microbiology, is an expert in bacterial genetics, genetic regulation and evolution. He studies Salmonella typhimurium, a bacterium found in soil and in the guts of birds and reptiles. Salmonella can cause food poisoning and typhoid fever when it infects humans. Recent work from his laboratory has provided support for a mechanism by which natural selection appears to direct mutations to useful sites. The process of generating a very rare favorable mutation can be divided into small steps, each of which improves growth slightly. This offers an explanation for the origin of new genes and the generation of some cancers. Roth is a member of the National Academy of Sciences and was on the faculty at the University of Utah before joining UC Davis in 2002. Contact: John Roth, Microbiology, (530) 752-6679, jrroth@ucdavis.edu.

Molecular clocks and the tree of life

Michael Sanderson, professor of evolution and ecology at UC Davis, develops mathematical models to determine rates of evolutionary change based on differences in DNA sequences between species. These so-called molecular clocks can run at uneven rates, because evolution does not seem to occur at a constant rate. Sanderson's laboratory is using these methods to build a family tree for the green plants. Sanderson also studies the problems in math and computing from handling very large sets of data in biology.

Steve Nadler, professor of nematology, uses DNA sequence data to study the family relationships of nematode roundworms, one of the most numerous, widespread and diverse groups of animals. Nadler's laboratory is collaborating with others across the country to set priorities and pursue work in using DNA analysis to build a nematode family tree. The research is part of a long-term effort, funded by the National Science Foundation, to build a 'Tree of Life' for all living things as envisaged by Charles Darwin in 1859. The complete tree will have millions of branches and may take decades to complete.

Contacts: Michael Sanderson, Evolution and Ecology, (530) 754-9229, mjsanderson@ucdavis.edu; Steve Nadler, Nematology, (530) 752-2121, sanadler@ucdavis.edu.

Genes, development and evolution

To make complex structures such as flowers, a liver or a leg, many genes have to work together at different stages of development. The groups of genes involved in making these structures often turn out to be very similar across different groups of plants and animals, relating evolutionary history to the development of individual living things. Several faculty members at UC Davis study these questions of evolution and development, or "Evo-Devo." For example, plant biologist Neelima Sinha recently showed that the same set of genes in all plants control whether they make simple or complex leaves. Among other UC Davis biologists, John Harada, Charles Gasser and John Bowman are studying how genes allow plants to make flowers, leaves, seeds and other structures.

Contacts: Neelima Sinha, Plant Biology, (530) 754-8441, nrsinha@ucdavis.edu; John Harada, Plant Biology, (530) 752-0673, jjharada@ucdavis.edu; Charles Gasser, Molecular and Cellular Biology, (530) 752-1013, csgasser@ucdavis.edu; John Bowman, Plant Biology, (530) 754-9652, jlbowman@ucdavis.edu.

Population genetics and DNA

David G. Smith, director of the Molecular Anthropology Laboratory at UC Davis, is an expert on the use of DNA to trace population origins and is frequently asked to determine whether or not specific prehistoric human remains are of Native American ancestry or to which modern tribal group a given set of Native American remains are ancestral. His research traces migrations of Native American tribes to and within the New World by comparing the DNA of modern peoples with that of prehistoric populations. Smith's second research interest is the use of DNA to reconstruct evolutionary relationships among different primate species, genetically manage captive animal colonies and identify genes that predispose non-human primates to diseases that are also common in humans. Contact: David G. Smith, Anthropology, (530) 752-6343, dgsmith@ucdavis.edu.

Media contacts:

• Andy Fell, News Service, (530) 752-4533, ahfell@ucdavis.edu
• Pat Bailey, News Service, (530) 752-9843, pjbailey@ucdavis.edu
• Claudia Morain, News Service, (530) 752-9841, cmmorain@ucdavis.edu

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