The value of a good editor

摘要

In 1958 Francis Crick, one of the codiscoverers of the double-helical structure of dna, spelled out what came to be called the "central dogma" of molecular biology. In a nutshell, this says that dna makes rna, which makes proteins. In other words DNA-which carries an organism's genetic code-"writes" that code into bits of rna, a similar, but not identical molecule. These then act as messengers which tell a cell's proteinmaking machinery what to make. It is a pithy and memorable summary. Sadly, reality is not quite so clear-cut. In a paper in Science, Sandra Garrett and Joshua Rosenthal of the University of Puerto Rico illustrate how the instructions in the dna are not always followed faithfully. The rna message can be rewritten before it is read. And that provides an extra opportunity for evolution to occur.Dr Garrett and Ms Rosenthal were studying octopuses, looking for differences between those that live in warm, tropical water and those that inhabit the poles. They concentrated on the make-up of the ion channels in the animals' cell membranes. These channels are cylindrical assemblages of protein molecules which help to control such things as the electrical activity of nerve cells and the release of hormones. The two researchers suspected that the channels found in warm-water species would not work well in the freezing temperatures that their polar cousins endure.