Introduction to DNA and RNA analysis
DNA and RNA analysis can be used to test groups of people with a disorder or
cancer to see if they have certain mutated genes in common. Pin pointing
these genes can open the doors to treatments that can cure or slow down the
disorder.
What’s the difference?
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Using the analogy of a car; DNA analysis allows you to put your ear up
against its hood to hear what is happening in the engine, and RNA processing is
like opening the hood and being able to see the engine itself.
A bit on DNA analysis
Using DNA processing one can know the location of genes that cause disorders
based on mutated genes people with the disorder have in common. A person has 3
billion bases from their mother, and three billion bases from their father.
99.9% of these bases are the same, and where these letters don't match up,
there lies a mutation. A mutation only arises about one letter every 1000
nucleotide bases (this is called single nucleotide polymorphism), and most of
the time mutations occur in DNA that doesn't code for anything (only about 1.5%
of DNA actually codes for proteins). DNA analysis is looking at the tiny base
changes someone has and comparing that information with other people with the
same disorder in order to find out which gene is mutated.
DNA analysis in use
For instance, on the X chromosome there is a particular DNA polymorphism
with two sites of spelling differences that differ in thymine and cytosine.
These sites happen to lie on the gene that codes for a particular protein
called apolipoprotein e on chromosome 19.There are three different spellings
that these two sites can have: CC, CT, and TC. If you happen to be homozygous
for the CC spelling (meaning that both the chromosome from your mom and dad
have this alternate spelling) then you have a 60 or 70% lifetime risk of
contracting Alzheimer's disease. About 3% of people are homozygous for
the CC spelling. Using DNA analysis you could find out whether or not you have
that spelling. Knowing that the apolipoprotein e is part of the biological process
that causes Alzheimer’s, scientists are making drugs that can slow down the production of that protein which in turn will delay Alzheimer's disease from your 60's to 70's
into your 120's and 130's.
RNA analysis
As DNA analysis is used to locate genes that cause disorders, RNA analysis
is used to look at what every gene’s specific job is (looking under the hood of
the car). Before RNA analysis was possible, scientists looked at multiple
patients' leukemia under a microscope and concluded that only one type of
leukemia existed. This didn't explain how some people did better on the
medications than others. As new technology arose (enzyme testing, cytology,
etc.), more evidence proved that there were indeed two different types of leukemia.
It took 40 years for scientists to declare that there were two kinds. Today they
are called AML and ALL, and they both have different treatments. Scientists
needed a faster and more efficient way of figuring this out so they could
discover more cancers that have multiple types and be able to treat them with
medications specific to their type. Using DNA microarrays scientists can pop
open the hood of the car and monitor every gene and its function instead of
just guessing.
So how do they do that?
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As if it wasn't complicated enough...
These DNA microarray chips consist of a little sliver of glass on which
there are little squares where 25 letter DNA sequences can be washed onto. To
get the DNA sequences on the chip they have a mask that covers all of the
squares except the ones you want to add a sequence to and they shine a light on
it. This makes the surface unprotected and makes it possible to wash on the
DNA sequence. Then you protect the surface and do the same to different squares
and wash DNA sequences on them until you have the DNA sequence you want in each
spot.
What can you do whith that?
The first spot could possibly have the complementary strand to the first
gene in the human genome, and the second spot the second gene and so on. These
would then be detectors to certain genes. After you could take some RNA from a
tumor and inject it into the chip. Each sequence of RNA will find its detector
or complementary strand of DNA that was laid out before. Then a scanner on the
chip will detect how much each gene is turned on and off based on the intensity
of that particular spot.
This information allows you to look at a tumor and
find out which genes are turned on in a group of test subjects who have a disorder, and therefore which genes are
responsible for that cancer or disorder. Back to Leukemia, the ALL tumors have
some specific genes that are turned on, and the AML tumors will have different
genes turned on. These differences clearly show a distinction between the two
types of Leukemia. Using these gene chips and the computer program that can
classify the types of leukemia based on genes that are turned on and off, the
ALL type of leukemia was further classified. It was
discovered that there are 3 types of leukemia: ALL1, ALL2, and AML. Using RNA
analysis like this, scientists can make a molecular taxonomy of all the tumors
and how they can be split into different types and how they differ and are the
same to each other.
