Research reveals role of gene in i...( somes not the jumble of chromosome fra...)

somes, not the jumble of chromosome fragments," Ma reports. "Because the chromosomes are not cut in the first place, you don't really need the RAD51 to repair it." These experiments demonstrate that RAD51 has an essential role in the biochemical repair of DNA during recombination. They also establish that this system for repairing broken chromosomes, which previously was known to occur in animals and fungi, occurs in plants, as well.

The RAD51 gene codes for a type of enzyme known as a recombinase, which catalyzes the swapping, or "crossover," of DNA sections between very similar, or "homologous" chromosomes. At conception, an individual inherits one copy of a chromosome from its father and another very similar but not exactly identical copy from its mother. This DNA swapping--a process known as recombination--is important for generating diversity among individuals within the same family and throughout the entire the population.

These very similar molecules of DNA, along which specific genes lie at the same point on each strand, are brought together by the molecular machinery of the cell to form a two-chromosome structure known as a homologous pair. Because the DNA along each chromosome is so similar, a thin structure is able to form between the chromosomes resulting in a structure known as a synaptonemal complex, which links the two strands together. Ma's research is the first to provide definitive evidence that the RAD51 gene is required specifically for homolog pairing and synapsis, in addition to its role in recombination during meiosis. "In the mutant, we found that the chromosomes do not come together to form pairs," he reports. "Our research shows that the RAD51 protein has a role in bringing a single strand of DNA to its counterpart within the nucleus of a cell to form a double-strand and is a critical component of the whole complex of proteins that holds the two strands close to one another."

Many of the findings of the
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Contact: Barbara K. Kennedy
science@psu.edu
814-863-4682
Penn State
21-Jul-2004

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