From DONALD MacPHEE
Andy Coghlan states incorrectly in his article entitled, ‘Are power
lines bad for you’ (11 April) that mutations in DNA can be repaired. Premutational
damage occurs in cellular DNA molecules and this is either repaired accurately
by repair enzymes – in which case further damage is averted – or inaccurately,
in which case new, heritable DNA sequences are generated. Because these
new DNA sequences are now copied very precisely when they are handed on
from parental cells to their offspring they are called mutations: as such,
they cannot be distinguished chemically from any other ‘correct’ pieces
of DNA, and hence they are are not subject to enzyme-mediated repair.
I also take issue with a quotation in the article asserting that ‘real
harm’ could result if the number of errors in DNA increases by as much as
0.01 per cent. In fact, research has shown that no harm appears to result
even if the numbers of background errors (as opposed to fixed, heritable
mutations) doubles or trebles.
Donald MacPhee La Trobe University, Melbourne, Australia
