QPMPA Journal September 2011 - Qualified Private Medical ...

science
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molecular biology
The interface where inorganic
is temporarily made organic!
Molecular biology, the interface between
organic and inorganic worlds,
arose from convergence of genetics,
physics, and chemistry on the common
problem: ‘structure and function of the
gene’. It is not so much a technique as
an approach. It searches for the molecular
plans below the large-scale
manifestations of biology. Biophysics
tries to study the molecules of life “from
the ground up”.
DNA coding of a protein is cloned. The
cloned plasmid has elements to drive protein
production and antibiotic resistance
markers to help follow it. This can be inserted
into cells; either integrated into the
genome or may remain independent of
the genome. In either case, the cell proteins
produced by stimulation of plasmid
can be studied. It can be tested for
enzymatic activity and activity of drugs
against it.
In the early twentieth century, mechanism
of gene reproduction and mutation
was unknown. Thomas H. Morgan used
fruit fly, Drosophila, to study the relationship
between gene and chromosomes.
Hermann J. Muller, recognized
“gene as the basis of life,” and discovered
Image of original DNA
the mutagenic effect of X-rays on Drosophila.
However, he recognized he was
limited in the extent to which he could
explicate the more fundamental properties
of genes and concluded, “The geneticist
is helpless to analyse the properties
further.”
The next decade saw several physicists
turning their attention to ‘inheritance’.
Erwin Schrödinger, proposed ways in
which quantum physics might account
dr. m. devadas
for the stability, yet mutability, of gene.
He speculated that the gene might be a
kind of irregular “aperiodic crystal” playing
a role in the “hereditary code-script.”
Max Delbruck became interested in the
physics of heredity after a lecture by Niels
Bohr, which expounded a principle of
complementarily between physics and
biology. In contrast to Schrödinger, Bohr
did not seek to reduce biology to physics,
but to understand how each discipline
complemented the other. And later
Delbruck admitted even the fruit fly was
too complex to unravel the enigma of life.
He chose bacteriophage instead. Delbruck
and another physicist-turned-biologist
Salvador Luria proved genes were not proteins
but DNA.
Linus Pauling utilized his knowledge of
structural chemistry to study macromolecular
structure of cell. Pauling investigated
weak forms of bonding, such
as hydrogen bonding, which were later
discovered to play important roles in proteins
and nucleic acids. Pauling also made
use of x-ray crystallography to investigate
molecular structure. X-rays bombarding
a molecule left unique photographic
images due to diffraction. Pauling
discovered the alpha-helical structure of
proteins and eventually set his sights on
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118
QPMPA.JMS . Vol. XXV . No. 3 . June-Sept. 2011