So often we read
in the press about the DNA test to be conducted
for the confirmation of a criminal’s identity
or a celebrity disowning a child or some such
story. People in general have a vague idea of
what DNA is. Most feel it is akin to the thumb
impression or teeth structure which is never the
same in any two humans. In this presentation we
will explain what exactly is meant by the use
of the term DNA. In doing so we will come across
a whole host of other equally difficult sounding
medical or chemical terms which need similar explaining.
We will look for meaning behind this high sounding
medical jargon. It will be our aim to make the
make the subject as easy as possible for the average
reader to comprehend.
Analysis
The acronym DNA stands for Deoxyribonucleic Acid.
The name is tongue twisting but is as unrevealing
as the abbreviation itself. Let us see whether
the following approach of describing/defining
characteristics would make more sense:
* DNA is called the molecular basis of heredity.
Knowledge of the DNA provides us with a map of
the human genome. The genome is the genetic code
of a human and his/her ancestors.
*DNA is the genetic material of all cellular organisms
and most viruses. DNA has within it the information
which directs protein synthesis and replication.
Protein synthesis means ‘production’
of the proteins needed by the cell or virus for
performing its activities and development. Replication
refers to the process by which DNA copies itself
for each descendant cell or virus, passing on
the information needed for protein synthesis.
In most cellular organisms, DNA is organized on
chromosomes located in the nucleus of the cell.
(DNA 1993-2003 Microsoft Corporation)
*DNA contains the information to make the cells
of all living organisms. (What is it? 2004)
* DNA is the fundamental building block for an
individual's entire genetic makeup. It is a component
of virtually every cell in the human body. Further,
a person's DNA is the same in every cell. For
example, the DNA in a man's blood is the same
as the DNA in his skin cells, semen, and saliva.
(What Every Law Enforcement Officer Should Know
About DNA Evidence 2004)
*DNA is the hereditary material that influences
the development and characteristics of each organism.
(‘Chromosome’1993-2003 Microsoft Corporation)
So now we do have some idea of what a DNA is.
Let’s move on. In one of the definitions
above it was said that DNA is organized on ‘chromosomes’
located in the nucleus (center, core) of the cell.
We will therefore explain what a chromosome is.
A chrosome of a DNA is a molecule (particle),
a microscopic formation, in the shape of a coil.
It is the chrosome that carries the molecule deoxyribonucleic
acid. (DNA 1993-2003 Microsoft Corporation).
The chromosomes form two chains or strands. Each
of these carries chemical compounds known as nucleotides.
These nucleotides are linked together to form
a chain. These chains, ladder like, are called
a double helix. A nucleotide has three parts:
a sugar molecule (deoxyribose), a phosphate group,
and four bases. The bases are adenine (A), guanine
(G), thymine (T), and cytosine(C). The sugar molecule
lies in the center with a phosphate group on one
of its side and a base on the other side. The
phosphate group of one sugar molecule is linked
to the phosphate group of the other sugar molecule.
The pairing of the sugar molecule and the phosphate
subunits make the parallel sides of the ladder
and the bases, facing inward; form the rungs of
the ladder.
The strings so formed contain information just
like a coded message. The information to make
specific molecules grouped into regions is called
genes. (What Every Law Enforcement Officer Should
Know About DNA Evidence 2004)
It will be useful to know a few other facts on
our topic. A protein is composed of smaller molecules
called amino acids, and the structure and function
of the protein is determined by the sequence of
its amino acids. How is a protein formed? It is
formed through the process ‘translation’
wherein the amino acids link together in a particular
sequence. Transcription is the process in which
a section of one strand acts as a template to
produce a new strand. Scientists can substitute
one DNA nucleotide with another containing a different
base. All descendant cells will change to the
altered nucleotide base sequence. The sequence
of amino acids in the resulting protein may also
be changed. Such a change in a DNA molecule is
called a mutation. (DNA 1993-2003 Microsoft Corporation).
The DNA strands in our body will be 500 million
miles long in a stretched out position! There
are millions of base pairs in each individual’s
DNA. Therefore we all have different DNA sequences.
(What is DNA? 2004)
DNA fingerprinting or DNA profiling is now accepted
in most courts in the United States. FBI has nation-wide
data base. This technique analyzes and compares
DNA from separate sources. The DNA samples can
be from hair, blood, semen, skin, saliva etc.
No two individuals, except twins, have the same
DNA. Therefore the sample will be statistically
distinctive. (Forensic Applications of Genetics
& DNA 2004)
Through recombinant DNA technology, scientists
can modify microorganisms so that they become
so-called factories that produce large quantities
of medically useful drugs. This technology is
used to produce insulin, interferon etc. Drugs
for treatment of cancer are also being experimented
under the DNA technology. We have already discussed
its use in the forensic field.
"Just as we have manipulated plastics and
metals, we are now manufacturing living materials"
said Lord Richie-Calder, a British science writer.
All this has been made possible by the ability
to isolate, identify and combine genes. There
are now so many genetically engineered agricultural
products like corn, soy and cotton. Even genetically
engineered insects, fish and domestic animals
have been produced. Big corporations have taken
control of the seed market, the agribusiness and
the agrochemical business. Genetically engineered
organisms reproduce, migrate and pollute the environment
and can infact run amok. There is a serious threat
to the ecosystem. However for the present there
is no science available for damage control. There
must be serious rethinking on the subject, public
debate ad enlightenment and then legislation to
regulate the unhindered rush for the genetic-engineered
‘bonanza’. (The Biotech Century 2004)
Conclusion/Summary
We have explained what is meant by DNA. Also what
do the various medical/chemical terms commonly
used on the topic mean. We have also briefly touched
upon the subject of application of the knowledge
gained from studies on DNA. We have seen the enormous
powerful forces released and to be released in
future scientists and researchers working on the
tissue culture or genetic engineering has been
revolutionary. There is need to go slow and the
common man must be made aware of the risks involved
so corrective measures can be introduced in time.
It is hoped that to this extent this paper helps
the reader.
|