The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
DNA microarrays, also known as "gene chips", refer to nylon membranes or glass slides that contain either synthetic oligonucleotide DNA or cDNA probes. Each probe has unique sequences that correspond to a specific gene. There are thousands of probes on one microarray, each less than 200 microns in size. The probes consist of either 20-25 oligonucleotide bases that are annealed to glass slides by laser photolithography, or cDNA sequences that are 500-5,000 bases long and are synthesized prior to immobilization onto the array.
Microarrays provide a tool to quantitate levels of gene expression for all genes in an organism. To determine levels of gene expression, scientists extract mRNA from the tissue or cell samples and reverse transcribe the extracted mRNA into complementary DNA (cDNA) and tag it with a fluorescent dye. The cDNA that corresponds to the gene sequence on the microarray will hybridize due to its complementary base pair sequence. The relative abundance of the specific cDNA measured by the amount of fluorescence provides a quantitative measurement of the level of gene expression, making it possible to simultaneously investigate characteristics of thousands of gene expression patterns in a single experiment.
Microarray technology allows scientists to research the molecular interactions of genes and gene products and can be used for gene discovery, disease diagnosis, drug discovery, and toxicological research. For example, if scientists can compare levels of gene expressed in normal cells to the genes that are expressed in cancer cells, it might lead to identifying genes that help to explain the cause of altered physiological or pathological processes that lead to the formation of tumors. Furthermore, gene expression patterns that are unique to certain tumors can be used for diagnostic purposes.
Microarrays can rapidly detect genetic variants, providing a genome-wide, genotype analysis. Additionally, genetic variants associated with disease, whether they are polymorphisms or gene mutations, can help diagnose single gene disorders, cancer susceptibility risks, as well as determine efficacy of drug treatments. Microarrays can also be used to identify a large number of specific DNA biomarkers such as single nucleotide polymorphisms (SNP), which can be used to determine genetic relatedness or for identifying markers that represent specific stages of disease.
The complex task of analyzing the massive amount of data generated by microarrays is often daunting. Algorithms and specialized computer programs are currently being developed to assist scientists in this task.