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Lab Times





to another thing in order to show or sug-

gest that they are similar”. For example,

when we speak of gene mapping, we use a

cartographic metaphor, likening genes on

chromosomes to positions on land maps.

Gross insists that such metaphors are cen-

tral to science because scientific research

programmes are largely focussed on estab-

lishing relationships.

Many metaphors in biology have turned

living cells and processes into their “pre-

sumed mechanical and computer coun-

terparts”, e.g. the heart is a “pump” with

“valves”, or a biochemical process is a “cas-

cade” that exhibits “feedback mechanisms”.

But such metaphors may in themselves af-

fect how science proceeds, especially if they

are imposed at the early stages of observa-

tion into phenomena. As the inquiry pro-

ceeds, initial metaphors can influence the

direction of research. Thus, while a bio-

logical object may initially be described by

analogy with a certain sort of mechanism,

subsequent effort will be directed at estab-

lishing, in greater detail, its precise work-

ings. In time, as enough work is accumulat-

ed along this line, the object will appear to

be that kind of machine. Gross notes that it

becomes very difficult to change this repre-

sentation once it is established.

Disputed definitions

There are many examples of disputes

in science that are language-based. Just

think of how much disagreement arises

when precisely defining the meaning of

keywords. The editors at



ed a list of some of the most contentious

words in science (Disputed Definitions,



2008 455:1023). They explained that

although science is supposed to be pre-

cise and measured, definitions can be frus-

tratingly vague and variable. From the life

sciences, their list included “race”, “stem

cell” and “consciousness” but let’s look at

the word “epigenetic”. This term has ris-

en sharply in popularity – its usage in Pub-

Med papers increased by more than ten-

fold between 1997 and 2007. A broad def-

inition of epigenetics is “the structural ad-

aptation of chromosomal regions so as to

register, signal or perpetuate altered activ-

ity states”. This definition was provided by

Adrian Bird, from the University of Edin-

burgh, who told


that “epigenetics is

a useful word if you don’t know what’s go-

ing on – if you do, you use something else”.

However, he admitted that this annoyed

some scientists, “The idea is that there is a

clear meaning and that it’s being violated

by people like me who use it more loosely.”

Mark Ptashne from the Sloan-Kettering

Cancer Center is one of those, who consider

definitions like Bird’s to be “preposterous-

ly dumb”. He says that it is so wide-ranging

that it includes pretty much every physi-

cal indicator of a gene’s activity. Ptashne

was the first scientist to demonstrate spe-

cific binding between protein and DNA, and

his lifelong work has been the elucidation

of the molecular mechanisms of the epige-

netic switch between the lytic and lysogen-

ic lifecyle of bacteriophage lambda. He fa-

vours the ‘traditional’ definition of epige-

netics as “a change in the state of expres-

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