Select Base-pair(s) by number

Click to load/re-load DNA sequence

Type the sequence number of the single base-pair you wish to select or of the series of base-pairs (for example 12-13), then press Enter/Return.

The display will zoom in on the base-pair(s) you have selected and they will be shown in ball-and stick representation using the color scheme shown below.
Hints:You do not have to look at every atom to decide which bases you are looking at:
  1. Bases with only one ring (6-membered) attached to the sugar are pyrimidines: C or T
  2. Bases with two fused rings (5- and 6- membered) attached to the sugar are purines: A or G.
  3. Remember that A pairs with T and G with C
  4. To find the 5' and 3' ends, look at the part of the sugar where the phosphates are connected; the 3' carbon is right on the sugar's ring and the 5' carbon is on a little 'arm'.