The bizarre case of the chromosome that never was
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SCIENTISTS were preening themselves last week as they unveiled
the genetic map of Chromosome 21, the second of the 23 packages of human
genes to fall to the power of the mighty sequencing machines.
Using these machines, scientists now know which of the sequences of the
33,800,000 chemical "letters" making up Chromosome 21 actually do anything
for we humans. It turns out that there may be as few as 225 sequences that
act as live, working genes - a startlingly low figure that has come as a
surprise to the scientists.
Still, time was when they didn't even know the number of
chromosomes in human cells, let alone what each
contained. Or, rather , they did know, but were too cowed by peer group pressure
to say what it was.
The bizarre case of the chromosome that never was dates back to 1923, when
the eminent American zoologist Theophilus Painter published a study in which
he confidently declared that there were 24 pairs of chromosomes in human
cells.
Others repeated the tricky microscopic observations, trying to avoid double
counting or missing any of these tiny packets of genes. They, too, claimed
to see 24 pairs of chromosomes.
But not everyone. Some found as few as 19, while others found 23. Still,
as everyone knew the correct answer was 24, those who got anything different
could be sure they had done something wrong.
Thus matters remained for the next 30 years, until scientists found ways
of placing cells onto microscope slides that helped separate the
chromosomes clearly. By 1956, it was obvious that
the textbooks were wrong: there are in fact 23 pairs of chromosomes in human
cells.
For all his confidence in his own abilities, Painter had blundered - but
worse than that, other scientists had preferred to bow to authority rather
than believe the evidence of their own eyes.Checking photographs of chromosomes
reprinted in textbooks, researchers later found that 23 pairs were clearly
shown - and yet captions under the photographs declared the figure to be
24.
Craven attitudes to authority are hardly confined to the biological sciences.
My favourite comes from the hardest of hard sciences, physics. The American
physicist Robert Millikan won a Nobel Prize in 1923 for his measurement of
the charge on the electron. Only years later did it emerge that he had hand-
picked his data to suit his own preconceptions of what the answer must be.
Millikan's result is now known to be too high. Such was his influence, however,
that subsequent measurements only slowly crept down towards the modern value;
no one being in a hurry to challenge the grand old man. This dismal example
of forelock tugging was later condemned as shameful by the
late Richard Feynman, another
Nobel prizewinning physicist.
Feynman went on to insist, however, that scientists don't do that sort of
thing any more.Such complacency is hard to square with the outcome of experiments
performed in the early Fifties by the American psychologist Solomon Asch.
Those taking part in the experiments found themselves sitting alongside five
other people. They were all shown a line of a certain length and asked to
state which of three other lines matched it.
Unknown to the subjects, all the other people in the room were stooges who
gave blatantly wrong answers. Yet such was the power of conformity that
three-quarters of them went along with the obviously false consensus at least
once.
Ever since, Asch's study has served as a warning to those who, like Feynman,
believe that the power of consensus is no more. In a nice twist, however,
Asch's conclusions have themselves come under fire in recent years.
In a series of hundreds of tests involving students in the early Eighties,
two British psychologists found only one case where the stooges succeeded
in bending a patsy to their consensus. As they concluded, this may reflect
the fact that today's students are more confident in their own views than
they were in the early Fifties.
Not that this conclusion has any hope of becoming the consensus, however:
other researchers have since confirmed Asch's findings, while still others
have found results some way between those of Asch, and those showing no
conformity.
It's enough to make one banker for the days when an eminent person just made
a pronouncement, so we could all move blithely on to other things.