Questions that have always intrigued you about the world will appear in this, your section,
and be answered by other readers. Please address your answers and questions to ‘Curiosities’.
How are the features added onto a globe? I can think of no convincing way that complex images could be printed directly onto a sphere without distortion or numerous joins.
A Coke can starts out as a disc with the painted artwork radially distorted – like one of those Victorian trick pictures that must be viewed in a cylindrical mirror. It is then pressed – or extruded – over a cylindrical mould and, presto, the familiar design appears in all its glory. I imagine the same process is used with a hemispherical press to make globes. And how fitting that a coke can should provide an example of the way in which a distorted view of the world becomes, via projection and manipulation, the standard model which shapes our perceptions!
Is it proven that long-lived creatures carry the same DNA throughout their lives?
Yes. When we are conceived the fertilized egg contains a full set of chromosomes. These contain the DNA that carries the instructions to make ‘us’ and all the proteins and enzymes our bodies need to survive. As the foetus grows, cells divide many times, each cell containing an exact copy of the original DNA. This process of cell division is called mitosis. It’s also the means by which, throughout our lives, we replace old cells that die. In theory each new cell is an exact copy of our original DNA.
However, the process of ageing may be caused by an accumulation of very minor errors that occur during mitosis – a sort of genetic ‘Chinese whispers’. As the errors in DNA replication accumulate the cells produced become less efficient.
No. Long-lived creatures do not carry exactly the same DNA throughout their lives because minor changes are always occurring. The changes aren’t large – human DNA for example remains recognizably human. But DNA changes occur because of mutations or copying errors. This DNA mutation is speeded up by toxic chemicals or radiation and pollution can be an important factor in this. Copying errors occur as bodies grow and DNA is copied into new cells. Consequently the older we are, the more cell divisions we have had – so the greater the chance that mistakes have happened. This is a bit like making a series of photocopies where each time the previous copy is the one used. The more copies you make, the more blurred the picture gets.
Fortunately, cells also contain complicated repair systems which check up on and fix damaged bits of DNA. However, the older we get the less effective are these repair mechanisms and some damage gets past them. This often leads to cancer. Obviously the longer we live the more likely we are to have such damaged DNA and that is why cancer is largely a disease of the old.
If changes occur to the DNA in the sex cells, in the ovaries or testes, then these changes can be passed on to offspring. Most DNA changes are the raw material of evolution. Unfortunately, though, some of these inheritable DNA changes are harmful and embryos containing them either die or produce children born with genetic diseases like haemophilia or muscular dystrophy.
awaiting your answers
Does anyone know how the Chinese custom of foot-binding originated?
Where are all the cows that supply 100-percent beef for all the McDonalds’ around the world? And who is sacrificing grain and water to this end?
When oil or gas is extracted does this not leave a cavity? Is it filled? And if so, by what?
Has anyone fully compared the costs of road transport against rail transport?
If you have any questions or answers please send them to Curiosities, New Internationalist, 55 Rectory Road, Oxford OX4 1BW, UK, or to your local NI office (see inside front cover for addresses).
THE VIEWS EXPRESSED IN THIS SECTION ARE NOT NECESSARILY THOSE OF NI.
©Copyright: New Internationalist 1996