When I joined SLS, I was asked to teach genetics. My heart sank. I had never done genetics. Vaguely, I remembered some classes during M.Sc but it never made any sense- more on how little I learnt in M.Sc. later. But the point was I did not know anything beyond Mendel's law- something I learnt in school. The senior faculty who coordinated the course was also emphatic that I should teach Benzer's experiments.
I sat down in the summer break to learn genetics. In an attempt to understand Benzer's experiments, I turned to the internet and thereby learnt about this book. I purchased it couple of years back and finally read it.
Frederic Lawrence Holmes was Professor and Chair for the Section of History of Medicine at Yale University. He draws on wealth of information to present an engaging picture of the emerging field of molecular biology. At the turn of last century, the nature of the hereditary material was plaguing the biologists. Thomas Morgan began using, what we call as classical genetic tools, to address this question using Drosophila. It was in his lab that Alfred Sturtevant, an undergraduate student forgetting his homework, built the first chromosome map one night. (This is a story I always tell my students!). Morgan himself was not comfortable about chromosomes as the unit of heredity- he preferred to use the term factors.
But was chromosomes composed of? And what was being transmitted?
Holmes paints the picture of those days- Muller's experiments with radiation to understand the nature of the chromosomes. The discovery that radiation induces mutation and what really is a mutation is something that Muller is obsessed with. He journeys from America to Russia to Scotland, changing the location of his labs as he bombards radiation on the chromosomes in a bid to understand the nature of the genetic material.
Into this milieu, Max Delbruck is sucked in after listening Niels Bohr's talk. He established the phage group- scientists working on bacteriophage in an attempt to understand genetics.
Seymour Benzer completes his Ph.D in physics and joins them as he wants to work on biophysics. He is enchanted with the phages and after a period in Delbruck's lab and a year in Paris with Andre Lwoff, he starts his own research group in Purdue. It is here he stumbles into a method to map the rII region (gene) of the T4 bacteriophage. It takes him from 1954 to 1961 to create a genetic map of the region. He shows that the rII gene is possibly divided into two regions and recombination between the two regions as well with a region was possible. This was the biggest contribution to the field of genetics.
But what most fascinated me was that fact that he kept a detailed record of that period. The work done everyday was recorded, analyzed, and a map drawn based on the results. Something I wish my students would emulate.
The second most fascinating fact was the usage of the word 'gene'.
Gene was first coined by Johannsen but geneticists could not agree what the term meant. The discovery that DNA was the genetic material followed by the structure of the DNA did little to dispel the fuzziness of the term. Benzer begins by using the term gene but is dissuaded by Alfred Hershey (of Hershey and Chase fame). So he coins three terms- Recon to define a unit of recombination, muton to define a unit of mutation, and cistron to define a unit of physiological action.
Unfortunately, Holmes was ill and dies before he could complete the story that he had originally conceived. So the book sort of ends abruptly with the question still hanging as to when did the word 'gene' find acceptability.
In most modern textbooks, Benzer's experiments are either not mentioned or are mentioned too briefly to understand its importance. Possibly in today's time, when sequencing so commonplace, it is not important. But his experiments were a major stepping block to our understanding of what a gene is.
I sat down in the summer break to learn genetics. In an attempt to understand Benzer's experiments, I turned to the internet and thereby learnt about this book. I purchased it couple of years back and finally read it.
Frederic Lawrence Holmes was Professor and Chair for the Section of History of Medicine at Yale University. He draws on wealth of information to present an engaging picture of the emerging field of molecular biology. At the turn of last century, the nature of the hereditary material was plaguing the biologists. Thomas Morgan began using, what we call as classical genetic tools, to address this question using Drosophila. It was in his lab that Alfred Sturtevant, an undergraduate student forgetting his homework, built the first chromosome map one night. (This is a story I always tell my students!). Morgan himself was not comfortable about chromosomes as the unit of heredity- he preferred to use the term factors.
But was chromosomes composed of? And what was being transmitted?
Holmes paints the picture of those days- Muller's experiments with radiation to understand the nature of the chromosomes. The discovery that radiation induces mutation and what really is a mutation is something that Muller is obsessed with. He journeys from America to Russia to Scotland, changing the location of his labs as he bombards radiation on the chromosomes in a bid to understand the nature of the genetic material.
Into this milieu, Max Delbruck is sucked in after listening Niels Bohr's talk. He established the phage group- scientists working on bacteriophage in an attempt to understand genetics.
Seymour Benzer completes his Ph.D in physics and joins them as he wants to work on biophysics. He is enchanted with the phages and after a period in Delbruck's lab and a year in Paris with Andre Lwoff, he starts his own research group in Purdue. It is here he stumbles into a method to map the rII region (gene) of the T4 bacteriophage. It takes him from 1954 to 1961 to create a genetic map of the region. He shows that the rII gene is possibly divided into two regions and recombination between the two regions as well with a region was possible. This was the biggest contribution to the field of genetics.
But what most fascinated me was that fact that he kept a detailed record of that period. The work done everyday was recorded, analyzed, and a map drawn based on the results. Something I wish my students would emulate.
The second most fascinating fact was the usage of the word 'gene'.
Gene was first coined by Johannsen but geneticists could not agree what the term meant. The discovery that DNA was the genetic material followed by the structure of the DNA did little to dispel the fuzziness of the term. Benzer begins by using the term gene but is dissuaded by Alfred Hershey (of Hershey and Chase fame). So he coins three terms- Recon to define a unit of recombination, muton to define a unit of mutation, and cistron to define a unit of physiological action.
Unfortunately, Holmes was ill and dies before he could complete the story that he had originally conceived. So the book sort of ends abruptly with the question still hanging as to when did the word 'gene' find acceptability.
In most modern textbooks, Benzer's experiments are either not mentioned or are mentioned too briefly to understand its importance. Possibly in today's time, when sequencing so commonplace, it is not important. But his experiments were a major stepping block to our understanding of what a gene is.
