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Editorial
S Mahadevan, Chief Editor
Our understanding of heredity received a substantial boost in the
1940s as a result of a string of major discoveries. ‘Classical’
genetics that flourished for four decades following the rediscovery of Mendel’s laws of heredity in 1900 provided a strong
quantitative framework to understand heredity even in the absence of knowledge about the chemical nature of the genetic
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material. The field of ‘molecular’ genetics was born when
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biologists started investigating the chemical identity of the gene.
The turning point that brought about the ‘molecular’ revolution
was the recognition that microorganisms can serve as paradigms to understand basic life
processes, exemplified by the discovery that DNA is the genetic material by Avery using the
bacterium Pneumococcus in 1944. What followed this epochal event was a remarkable series
of path-breaking findings that expanded our understanding of life processes at the molecular
level. These findings led to the realization that there is substantial conservation of molecular
mechanisms across diverse living organisms, such as the processing of genetic information,
revealing an evolutionary thread that binds all life on earth.
One of the contributors to this scientific revolution was William Hayes who followed the work
of another pioneer, Joshua Lederberg, whose classic experiments showed that bacteria also
have the capability to exchange genetic information via a sexual process termed conjugation.
While Lederberg believed that the transfer of genetic information among the partners was
bidirectional, Hayes’ elegant experiments demonstrated that exchange of genetic information
during conjugation was unidirectional. The asymmetry in the process led to the concept of
‘male’ and ‘female’ strains in bacteria, determined by the presence or absence of a hypothetical genetic element termed as the Fertility factor or F factor. This breakthrough was the
starting point for the detailed genetic analysis of bacteria which was essential to many future
discoveries such as gene regulation. Hayes belongs to the rare group of scientists, Mendel
included, who published very few papers, but what they published made such an impact for
many decades to come, driving home the fact that ultimately it is quality – not quantity – that
matters in science.
RESONANCE  October 2011
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