Human Genetics Problem Set

Problem 18 Tutorial: DNA expressed as mRNA transcripts

Which of the following is a marker for regions of the DNA expressed as mRNA transcripts, and characterized by cDNA cloning?

EST To characterize sequences from the human genome that are coding regions for mRNAs (i.e. "expressed" sequences), cDNA copies of mixtures of cellular mRNA templates are synthesized with reverse transcriptase. The cDNAs can be converted to double stranded cDNAs, inserted into plasmid vectors using recombinant DNA technology, purified by cloning in bacterial cells, and sequenced.

The term "EST" is now used to describe the DNA sequence of a short fragment of a cDNA. As of October 1996, there were about 450,000 EST sequences from human DNA in public DNA sequence databases. Many are redundant cDNAs from different regions of the same mRNA. Nevertheless, approximately 49,000 unique human ESTs are known, representing half of the predicted 100,000 expressed sequences in the human genome.

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Revised: November 5, 1998
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