Monday, 28 May 2012

The passive gene

In every living organism there are cells and in the nucleus of each cell,  as well as other parts of the cell, there are stored instructions on how the cell should behave in certain situations, depending on

  • The environment inside the cell

  • Other cells within the organism

  • The world external to the organism

According to the latest research in epigenetics  there is a startling fourth causative factor – the environment and food intake of the organism’s ancestors, to at least several generations. See The epigenetics revolution by Nessa Carey.  The author has produced an excellent website on epigenetics which stands on its own as a brief introduction: a whistlestop tour of epigenetics.

The nucleus comprises a microscopic strand of DNA which is folded around a compact complex of 8 protein molecules called histones. A vast array of instructions is coded in the DNA’s double helix, in segments called chromosomes and subsegments of chromosomes called genes.  Typically there are a few hundred genes per chromosome. The complete sequence is called the genome. A small proportion of the genome comprises genes which, when ‘told’ to do so in a highly organised process of cutting, splicing, tranferring, repairing and editing across billions of base pairs (the units which store the information, like 1's and 0's in a computer), initiate, but do not enact, the manufacture of proteins in the right place at the right time; but most of the these genes are either little understood or a total mystery. 98% of the human genome was conveniently, perhaps arrogantly, labelled ‘junk’ until only a decade or so ago, on the grounds that they did not appear to have anything to do with the production of proteins. 

What is often overlooked in popular science documentaries and books is that the gene is only a passive set of instructions. The essence of biological life is the way these instructions are formed, passed on from generation to generation and read by a complex of protein molecules in such a way as to allow the building and functioning of the host organism (e.g. you or I). The gene does nothing. It is no more the essence of a living organism than a book on how to make a car or repair it are functional parts of a motor car or an automobile factory or an automobile R&D operation.  What is fantastic is how the book of life was written, is continually being rewritten and edited, together with the extraordinary process by which it is read and used to make, maintain and repair a living, adaptive organism.

Three examples to put the gene in its place:

The honey bee
It is well known that a honey bee colony comprises a queen, female workers and males which mate with the queen. What is less well known is that every bee of every type in the honeybee colony, whatever its role or physical structure, is genetically identical. Some incredible process occurs by which totally different organisms with different functions (such as gathering pollen or mating), grow out of the same DNA with the same genes in the same chromosomes, depending on how some agency picks out the right biological instructions at the right time to allow the organism to fulfil its role in the colony. Even the food eaten affects the development of a bee – e.g. royal jelly, made from pollen and nectar collected by workers, is fed selectively to certain female bees and somehow causes them to become queens. These facts are only the tip of a very large iceberg. Collectively the process can only be called miraculous, yet the genes are not the drivers.

The butterfly
It is also well known that a butterfly starts life as a caterpillar. What two organisms could be more different? Yet, again, they are genetically identical. The same genes are used in entirely different ways in the butterfly from when they reside in the caterpillar. The two creatures look different, have different survival strategies and different predators. One flies through the air, the other crawls painfully slowly over vegetation. A fly and the maggot from which it emerges also have exactly the same genes.

People and worms
We have about 20,000 genes, the same as a worm.  But look at the difference. We each have trillions of cells in hundreds of complex organs, all cleverly and intricately orchestrated and in balance with many more bacterial cells which form part of us, the whole system being in balance with the environment. The worm, albeit an engineering masterwork, contains only a thousand cells and relatively rudimentary organisms.

Genes are not even self-replicators - the information is passed on to the next generation by a copying process originating outside the gene and precisely how this is done is not understood.  They do not 'decide' to replicate or copy themselves- they do not have free will. They are neither selfish nor altruistic but part of a miraculous process.