JOSHUA LEDERBERG 
every adult cell, 5 thousand million paired nucleotide units long. 
This store of “information”? could specify 10 million kinds of 
proteins. Almost certainly, most of this information controls 
just when and where some few thousands of proteins will be 
made—the tendons and enzymes, antibodies, hormones and the 
like, of which the body is composed. 
Evolution is the duplication and exploitation of structural 
error. Simple organisms have as few as 100,000 units (the even 
simpler viruses plagiarize the larger genetic “library” of their 
host cells). Mistakes in molecular reproduction—mutations— 
are inevitable: one of evolution’s marvels is that they are so rare. 
The innovation rarely serves better; when it does, the cell that 
carries the mutant DNA will be favourably selected, and the 
new DNA thus preferentially propagated in future generations. 
From principle to detail is still a big step. We do not in fact 
yet know the actual nucleotide sequence of any gene. Only in 
micro-organisms, whose DNA content is from a millionth to a 
thousandth of man’s, can we momentarily substitute one DNA 
molecule for another in the genetic composition of a cell, and 
then inferentially judge the chemical differences between them. 
But a little inspiration and reasonable effort will be rewarded 
by detailed knowledge of genetic structure, very soon for mi- 
crobes, no more than a decade or so away for parts of the 
human genome. 
EUGENICS AND EUPHENICS 
Most geneticists, however they may be divided on their 
specifications for policy, are deeply concerned over the status 
and prospects of the human genotype. 
Human talents are widely disparate; much of the disparity 
(no one suggests all) has a genetic basis. The facts of human 
reproduction are all gloomy—the stratification of fecundity by 
economic status, the new environmental insults to our genes, 
the sheltering by humanitarian medicine of once-lethal defects. 
Even if these evils were tolerable or neutralized or mis-stated, 
do we not still sinfully waste a treasure of knowledge by ignoring 
the creative possibilities of genetic improvement? Surely the 
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