A cell devotes a significant amount of effort to maintaining the stability of its genome, preventing the sorts of chromosomal rearrangements characteristic of many cancers.
Assays that measure the rate of gross chromosomal rearrangements (GCRs) are needed in order to understand the individual genes and the different pathways that suppress genomic instability. In the September issue of Cold Spring Harbor Protocols, Richard Kolodner and colleagues from the University of California, San Diego's Ludwig Institute for Cancer Research present "Determination of Gross Chromosomal Rearrangement Rates," a genetic assay to quantitatively measure the rate at which GCRs occur in yeast cells.
The assay measures the rate of simultaneous inactivation of two markers placed on a nonessential end of a yeast chromosome. This simple protocol for determining GCR mutation rates in a variety of genetic backgrounds coupled with a diversity of modified GCR assays has provided tremendous insight into the large numbers of pathways that suppress genomic instability in yeast and appear to be relevant to cancer suppression pathways in humans. This featured protocol is freely available on the journal's website.
Large segments of DNA can vary in copy number between individuals. Such copy number variations (CNVs) contribute greatly to genetic diversity and are also thought to be associated with susceptibility or resistance to some diseases, including cancer. "Simple Copy Number Determination with Reference Query Pyrosequencing (RQPS)," featured in the September issue of Cold Spring Harbor Protocols, provides an assay for determining the copy number of any allele in the genome. The method, from Raphael Kopan and colleagues at Washington University, takes advantage of the fact that pyrosequencing can accurately measure the ratio of DNA fragments in a mixture that differ by a single nucleotide. A reference allele with a known copy number and a query allele with an unknown copy number are engineered with single nucleotide variations, and the ratio seen between these probes and genomic DNA reflects the copy number. RQPS can be used to measure copy number of any transgene, differentiate homozygotes from heterozygotes, detect the CNV of endogenous genes, and screen embryonic stem cells targeted with bacterial artificial chromosome (BAC) vectors. RQPS is rapid, inexpensive, sensitive, and adaptable to high-throughput approaches. The article is freely available on the journal's website.
About Cold Spring Harbor Protocols: Cold Spring Harbor Protocols (www.cshprotocols.org) is a monthly peer-reviewed journal of methods used in a wide range of biology laboratories. It is structured to be highly interactive, with each protocol cross-linked to related methods, descriptive information panels, and illustrative material to maximize the total information available to investigators. Each protocol is clearly presented and designed for easy use at the bench—complete with reagents, equipment, and recipe lists. Life science researchers can access the entire collection via institutional site licenses, and can add their suggestions and comments to further refine the techniques.
About Cold Spring Harbor Laboratory Press: Cold Spring Harbor Laboratory Press is an internationally renowned publisher of books, journals, and electronic media, located on Long Island, New York. Since 1933, it has furthered the advance and spread of scientific knowledge in all areas of genetics and molecular biology, including cancer biology, plant science, bioinformatics, and neurobiology. It is a division of Cold Spring Harbor Laboratory, an innovator in life science research and the education of scientists, students, and the public. For more information, visit www.cshlpress.com.
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