The story as told by Cobb falls into a number of phases. Prior to 1953 there was much debate about the chemical nature of genes. Many influential biologists were convinced that genes were proteins. The duplication of chromosomes during cell division was known and it was also known that they consisted of DNA, but this molecule didn't seem to most scientists to be complex enough to carry the genetic information needed to explain heredity. Oswald Avery was an exception; his meticulous research pointed the way forward but he encountered a lot of opposition. On his death in 1955 a brief obituary in The New York Times didn't mention his work on DNA,
Avery's findings now look so obvious and yet many scientists at the time responded to them with hostility or bemusement.
Even the discovery of the structure of DNA by Crick and Watson did not immediately convince everyone that proteins were not involved in genes. In part this was because although most scientists now recognised that DNA must contain the information needed to construct proteins, how this happened was still unknown. The unscrambling of what came to be known as the DNA code constituted the second phase in the story. It turned out to be lengthy and difficult, because it was initially tackled in the wrong way.
For a long time, attempts to understand how the coding worked were shaped by theoretical physicists such as George Gamow and by scientists and mathematicians involved in cybernetics and information theory. Sophisticated explanations were produced but all of them eventually proved to be wrong; the answers finally came from biological experiments, not abstract reasoning.
None of the theoretical codes dreamt up by theoreticians were correct, because they made assumptions that were logical, rigorous and hopelessly wrong. The physicists' appetite for elegance and the biochemists' naïve assumptions about natural selection led them to assume that the code had to be extremely economical, that it would look as though it had been designed along logical principles. But that is not how biology works. The genetic code is a product of biology and messy, illogical and inelegant. ... As [François] Jacob put it in 1977, natural selection does not design, it tinkers with what is available.Scientists who work in genetics often talk of the genetic code as containing information that enables the production of proteins. But Cobb explains that this is not the same as information in the mathematical sense, As used by geneticist it is a useful metaphor that helps to shape their thinking rather than an exact description.
The deciphering of the code was a huge advance in our understanding. In 1966 John Cairns, the director of Cold Spring Harbor Laboratory, said that this must be without parallel in the history of biology. But as Cobb explains in his later chapters, the picture has had to be revised in a number of ways.
One of these was the discovery of prions, which are infective agents that work by modifying the shapes of proteins. Prions are themselves proteins and this might seem to challenge the 'central dogma' which states that proteins can only be changed by information coming from nucleic acids. However, there is no contradiction of the dogma because the infective prions don't alter the amino acid sequence of the proteins they modify, which is what the cental dogma forbids, but only alter their shape.
Other new discoveries discussed by Cobb include so-called junk DNA (the large amount of genetic material that has no known function) and epigenetics, which is sometimes hyped as posing a challenge to orthodox Darwinian evolution. Cobb does a good job of bringing order to this often confusing subject. Essentially, epigenetic effects are examples of gene regulation, which determines whether genes are active or not. In rare cases such effects can be transmitted between generations, but this does not alter the fundamental mechanism of evolution.
Finally, Cobb looks to the future. It seems that the era of individuals or small groups making radical innovations has probably passed, and from now research will be the product of large multinational teams in which each member contributes a circumscribed amount to the result.
An ever-increasing quantity of research is now concerned with genetic engineering which is by no means free of risks or ethical problems. Writing five years before the current Covid-19 pandemic, Cobb was concerned by the likelihood of a lethal flu outbreak triggered by dangerous research.
In June 2014 a group of US and Japanese scientists...attempted to recreate the Spanish Flu virus, which killed millions of people after the First World War. As is well known, we are in danger of another global flu epidemic with avian flu being the most likely source because it seems also to have been the source of the Spanish Flu.Many researchers around the world were appalled by this work, describing it as madness and folly. As one virologist remarked, 'if society, the intelligent layperson, understood what was going on, they would say "What the F are you doing?"'
Cobb has given us a remarkably rich, readable, and revealing account of the origin and development of modern genetics. But more than this, his book provides insight into the scientific process more generally, particularly as regards the role of metaphor in scientific thinking.
Although experimentation is generally the most powerful way of obtaining evidence that can test a hypothesis, to interpret this evidence we need theories and conceptual frameowrks, which in turn are made up of words and metapbors and analogies. Understanding the power and limits such metaphors will help us prepare for the breakthroughs of tomorrow, where we will interpret what we know and discover what we have yet to imagine.
21-06-2020