DNA bases
Although these 4 images are rotatable in 3 dimensions, it is very noticeable that each molecule is in fact flat!
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reminders about DNA.
In each case, an asterisk marks the position (H atom removed) when the base attaches to C1 of deoxyribose by condensation.
Numbers represent atoms between which hydrogen bonds form across the centre of the DNA molecule (2 such hydrogen bonds in the case of A-T and 3 in the case of C-G).