RNA bases

RNA bases - rotatable in 3 dimensions

Purines Pyrimidines
The only difference between DNA and RNA bases is that uracil replaces thymine. Uracil is like thymine - but without the methyl group (-CH3) at the 5 position. In interactions between mRNA and tRNA:
Adenine (A) always pairs up with Uracil (U);
Guanine (G) always pairs up with Cytosine (C).
This pairing also occurs in sections of RNA where the molecule bends back on itself to become double stranded.

Although these four images are rotatable in 3 dimensions, it is very noticeable that each molecule is in fact flat! Click here to turn all 4 through 90 ° to show them from the edge - 3 more clicks to return to the start position!

In each case, an asterisk (*) marks the position where the base attaches to C1 of deoxyribose by condensation (H atom removed).

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).

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