Microarrays allows the identification of organisms in an ecological sample by hybridizing DNA extracted from the sample to a set of known DNA specimens arrayed on a solid support, usually a microscope slide (reviewed in Call et al. 2003). The sample DNA, or more usually PCR product derived from it, is labeled with a fluorophore so that the specific sites of hybridization on the microarray can be visualized and the intensity of the hybridization signal quantified. The method is conceptually identical to Southern hybridization of a dot blot, but technological innovations allow thousands of known DNA samples to be arrayed on a single microscope slide and many such slides to be produced in a single batch at low cost.
Showing posts with label microarrays. Show all posts
Showing posts with label microarrays. Show all posts
Dna Array
Pat Brown developed a technique where cDNAs can be embedded onto lass slided.Using these DNA arrays,he could do large-scale expression studies
div style="text-align: justify;">Growth stage-specific mRNA are isoloated,and then reverse transcribed to give inique cDNA populations.These are directly embedded onto specially cated gass slides. These slides are coated with poly-lysine,which is positively charged.DNA is negatively charged,so that cDNA "sticks" to the slide through an ionic interaction.The cDNA can still interact with DNA probe.
Brown used srrays to obtain gene expression profiles of cancer.Diffuse large B-cell lymphoma(DLBCL) is a common lymphoma-cancer of the lymp nodes.He found sub-types of DLBCL that correlated with survival rates.
Brown made a chip with genes expressed by the lymph nodes and those importtant in cancer biology .a total of 17856 cDNA genes were printed onto what we called "lymphochip".Remember ,each square on teh chip corresponds to a differnt cDNA.
Then ,he made CDNAs from different DLBCL tumors.
He labelled one set of cDNA with a red florescent tag;the other with a green tag.
Brown incubated the arrays with the tagged cDNAs, which bound to the matching genes printed on the array.
Since he knew the positions of the genes on the DNA array,Brown could figure out the levels of gene expression based on the color signal.If the gene was only expressed in DLBCL1 cells,the square was red.similarly ,of the gene was only expressed in DLBCL2 cells,the square was green.If the gene was expressed equally in both cells,the square was yellow
Thus ,brown identified two sub-types of DLBCL-GC B-like and Activated B-like DLBCL.These sub-types have different responses to the therapy,and with this type of diagnosis,more tailored treatment can begin for patients.This type of tailored treatment is called "pharmacogenomics."
Brown can also analyse the differences in gene expression for these two very similar lymphomas.This may give better understanding of how cancers work, and hopeflly develop beter therapies and cures.
