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Expressed Sequence Tags (ESTs)

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Tayler Massey

on 6 July 2013

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Transcript of Expressed Sequence Tags (ESTs)

Expressed By: Tayler Massey and Victoria Peltonen Sequence Tags (ESTs) What Are ESTs? Small pieces of DNA sequence (usually 200-500 nucleotides) which are created by sequencing one or both ends of an expressed gene. A tiny portion of an entire gene that can be used to help identify unknown genes and to map their positions within a genome. Process: From DNA to an EST 1. Take DNA and convert it to mRNA through translation - mRNA doesn't include non-coding regions between genes or introns so the only info left is the desired gene information 2. Outside of cells mRNA is unstable so scientists use the reverse transcriptase enzyme to convert the mRNA into cDNA 3. The cDNA is sequenced at one or both of its ends, whose sequenced nucleotides become the ESTs Two kinds of cDNA ESTs... A 5' EST, formed from the front end of cDNA, codes for proteins. These regions are often conserved through species and don't change very much within gene families. A 3' EST, formed from the back end of cDNA, many times falls in the category of UTR or an untranslated region. UTR areas of a gene are not translated into proteins, and for that reason such ESTs are not usually conserved through multiple species. Uses of ESTs Gene Discovery Resources Genome Landmarks A gene family is a group of closely related genes that produce simiar protein products. ESTs are powerful tools in the hunt for known genes because they greatly reduce the time required to locate a gene. Using ESTs, scientists have rapidly isolated some of the genes involved in Alzheimer's disease and colon cancer. Method:
scientists first use observable biological clues to identify ESTs that may correspond to disease gene candidates
then examine the DNA of disease patients for mutations in one or more of these candidate genes to confirm gene identity scientists searching for genes need genome maps to help them to navigate through the billions of nucleotides that make up the human genome map must include markers best current technique to do so is STS mapping or Sequence taggs mapping a STS is a short sequence of DNA that is easy to recognize and is only found in one genome an EST acts as a STS, many times the 3' EST because of their exclusiveness to single species The End!
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