Name: Karen L.
Date: March 2004
How is reverse transcriptase used in molecular biology?
and could you give me an example?
Reverse transcriptase copies RNA to DNA. It is often used to make a "library" of
DNA clones from RNA. Let's say you are interested in studying only the genes that
are expressed in a newly-fertilized frog embryo. First, you isolate the messenger
RNA from the embryo. Now you use reverse transcriptase to make DNA copies of the
RNA. Then you clone the DNA pieces into some type of vector, such as a plasmid or
phage. Now you have a stage-specific library. Every clone in the library is there
because it encodes an RNA that is expressed in your newly-fertilized embryos. This
is very different from a total genomic library, which should represent all of the
DNA in the nucleus, regardless of when it is expressed.
Paul Mahoney, PhD
There are lots of uses, but one simple example is reverse transcribing an mRNA message
back into DNA. mRNA is very unstable, but it has already been processed, ie. it has had
the introns removed. So it is a complete protein "recipe" without the interrupting
sequences in it. Reverse transcriptase is used to turn it back into DNA but without the
introns. This DNA is called cDNA or copy DNA. Then it can be used for study. For
example one thing they use copy DNA for is as a "probe" for finding where in the genome
that mRNA came from. If the DNA is made to be single stranded, the half that is opposite
will stick to the place in the DNA that the gene is found.
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