Chargaff's Rules

    Given the accepted tetranucleotide hypothesis, most workers assumed that deviations from equimolar base ratios were due to experimental error. Erwin Chargaff (1905 - 2002) 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, with [C+G] is less abundant. These ratios are referred to as "Chargaff's Rules".

    The molar equivalences of A vs T and C vs G intuitively suggest some sort of pairing relationship. Chargaff himself refused to speculate on the implications of his empirical observations in the absence of further experimental evidence, and regarded Watson & Crick's model building as a scientifically unsound 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.

All text material ©2015 by Steven M. Carr