(Warning! Reading before the book may spoil your enjoyment!)
Lamarck was a French Naturalist, and a man ahead of his time. I remember being taught about Lamarck in A’Level Biology, but only because his theory of evolution was deemed to be a curiosity. Darwin’s theory of natural selection was so overwhelmingly supported by the evidence, it was as if people felt duty-bound to try and balance it in some way, and Larmarck was the only real alternative. But there was no basis, even 20 years ago, to support his theory of heritability.
In a sense, though, he pre-empted Darwin. Conceptually, the possibility that the experiences of an organism’s life could determine something of the life of it’s offspring is akin to Darwin’s observations. What Darwin did was understand how this came to be, through natural selection. While Lamarck hypothesised that this transfer of survival advantage happened directly, from organism to organism, rather than through environmental pressures over much longer periods of time.
It turns out they were both right. But Lamarck’s theory had to wait for science to evolve considerably before it re-emerged as a credible addition to our understanding of inheritance. The biological mechanism by which the experiences of an organism could be heritable have been revealed by a theory of genetic control called epigenetics. It’s not clear exactly how this happens, but the evidence is increasing for its existence. And the link to Lamarck has been made by a number of observers.
Briefly, epigenetics describes a series of mechanisms that control which genes are expressed or active in a cell at any one time. And it seems that as cells (and then ultimately whole organisms) experience changes in the environment, these control mechanisms become imprinted or altered. And some of these alterations can be passed on to the next generation. Its quite spooky stuff when you think about it. And Daniel starts to do just that in Antisense.
Techniques to study genetics
Studying the activity of genes is at the heart of inheritance and genetics. We’re all familiar with the concept of a genetic code that we inherit, but there are multiple levels of control that determine how those genes function in any given cell, tissue or organism i.e.; us. And it’s this control, as much as variations in the genetic code itself that shapes the vast array of different species and individuals the planet hosts today.
This technique to study RNA is a little out of date now, having been largely replaced by the polymerase chain reaction or PCR, but given Antisense is set a little in the past it suited my purposes, being more visual. Those black blobs on the picture above are where a piece of RNA and an antisense ‘probe’ (see below) have bound to each other. More details.
If you think of RNA as being a series of ‘locks’ that come in one of four varieties (U A C G), this is the ‘sense’ sequence (blue in the picture below). Then one can make a complementary sequence of ‘keys’ (G C A U) or an antisense probe that will bind to those locks and recognise it (red in the picture below).
There are thousands of different sequences of RNA in any one cell, but they are each unique in some way. So by designing the complementary antisense probe sequence the right way, one can tag an individual RNA sequence fairly easily. What a Northern blot does is allow these sense/antisense combinations to be visualised as they are slightly different weights and electrical charges, and one can separate them using an electrical current. More detail, as ever, can be found on good old Wikipedia. This link also describes how these antisense sequences or probes can be used as drugs to block the function of the RNA. Cool.