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When genes are activated, the instructions encoded within their DNA are first transcribed into a related molecule called RNA. Shepherd’s colleague Elissa Pastuzyn showed that the Arc shells can enclose RNA and move it from one neuron to another. And that’s basically what retroviruses do—they use protein shells to…
The awesome power that genetic engineering will one day place in our hands was foreshadowed recently by some experimenters at the University of Basel in Switzerland. Walter Gehring and his students were studying the effects of the eyeless gene in fruit flies. The gene is called eyeless because its absence causes flies…
The standard DNA 'prism' is a gel electrophoresis column, that is, a long tube filled with jelly through which an electric current is passed. A solution containing the scissored stretches of DNA, all jumbled together, is poured into one end of the tube. The DNA fragments are all electrically attracted to the negative…
Anomaly (2) was observed by Fred Griffith, decades before DNA and the genetic code. He found that if you inject a heat-treated, dead, virulent species of bacteria (pneumococcus S) into a rat previously infected with a nonvirulent species (pneumococcus R), then species R became transformed into species S, thereby…
It’s a common misconception that chimp DNA differs from Homo sapiens sapiens genes by only a single percent, but this number is apocryphal. In actuality, the degree of similarity of human and chimp genetic code depends mostly on how you count. Since all complex organisms from Earth possess great swaths of junk DNA…
Parasites are not only incredibly diverse; they are also incredibly successful. There are parasitic stretches of DNA in your own genes, some of which are called retrotransposons. Many of the parasitic stretches were originally viruses that entered our DNA. Most of them don't do us any harm. They just copy and insert…
The messages that DNA molecules contain are all but eternal when seen against the time scale of individual lifetimes. The lifetimes of DNA messages (give or take a few mutations) are measured in units ranging from millions of years to hundreds of millions of years; or, in other words, ranging from 10,000 individual…
It is raining DNA outside. On the bank of the Oxford canal at the bottom of my garden is a large willow tree, and it is pumping downy seeds into the air. ... [spreading] DNA whose coded characters spell out specific instructions for building willow trees that will shed a new generation of downy seeds. … It is raining…
We are now witnessing, after the slow fermentation of fifty years, a concentration of technical power aimed at the essential determinants of heredity, development and disease. This concentration is made possible by the common function of nucleic acids as the molecular midwife of all reproductive particles. Indeed it…
My own thinking (and that of many of my colleagues) is based on two general principles, which I shall call the Sequence Hypothesis and the Central Dogma. The direct evidence for both of them is negligible, but I have found them to be of great help in getting to grips with these very complex problems. I present them…
Haemoglobin is a very large molecule by ordinary standards, containing about ten thousand atoms, but the chances are that your haemoglobin and mine are identical, and significantly different from that of a pig or horse. You may be impressed by how much human beings differ from one another, but if you were to look into…
We know from X-ray diffraction studies that a strand of DNA is 1.5 nanometers (1.5 x 10 to the -9 meters) in radius. Assume a cylinder 1 meter long (the arm's length) with a radius of 1.5 nanometers and work out the volume (length x pi r-squared). A typical animal cell is about 8 micrometers (8 x 10 to the -6 meters)…
Knowing what we know from X-ray and related studies of the fibrous proteins, how they are built from long polypeptide chains with linear patterns drawn to a grand scale, how these chains can contract and take up different configurations by intramolecular folding, how the chain- groups are penetrated by, and their…
Brain wiring begins with the outgrowth of axons. Once a newborn neuron has migrated, planting its cell body in a permanent position, it sends out a fine axon shoot with an enlarged tip known as a growth cone. At the end of the growth cone are about a dozen long tentacles that shoot out in all directions and act like…
Each individual's genome, in any one generation, will be a sample from the species database. Different species will have different databases because of their different ancestral worlds. The database in the gene pool of camels will encode information about deserts and how to survive in them. The DNA in mole gene pools…
Textbooks of biology repeat time and again that DNA is a 'blueprint' for building a body. It isn't. A true blueprint of, say, a car or a house embodies a one-toone mapping from paper to finished product. It follows from this that a blueprint is reversible. It is as easy to go from house to blueprint as the other way…
...there is a distressingly long list of people who have been wrongly convicted on eye-witness testimony and subsequently freed - sometimes after many years - because of new evidence from DNA. In Texas alone, thirty-five condemned people have been exonerated since DNA evidence became admissible in court. And that's…