Given the accepted tetranucleotide hypothesis, most workers assumed that deviations from equimolar base ratios were due to experimental error. Erwin Chargaff (1905 - 19) showed experimentally that base compositions actually varied among species, however in all species the molar ratios [ A ] = [ T ] and [ C ] = [ G ], and that the ratio [C+G] / [ A+T ] was typically less than unity (that is, [C+G] is less abundant). These ratios are referred to as "Chargall's Rules".
equivalences of A vs
T and C vs
intuitively suggest some sort of pairing
Chargaff himself refused to speculate on the implications of his
observations in the absence of further experimental evidence,
and regarded Watson & Crick's model building as a
approach. Chargaff subsequently denigrated molecular biology in
general, and became embittered over what he regarded as failure
to acknowledge the importance of his data.
HOMEWORK: Several generations of genetics students have said to themselves, "Two strands or three, bases inside or outside, and you have Chargaff's Rules - how long can it take?" Is this an accurate statement of the state of things at Cambridge in 1952.