A Piece of a DNA Molecule

Note: To view these molecular models, you need the plug-in CHIME, which can be downloaded free from MDL. Check out the directions for using CHIME if you need them.

Here are two views of a portion of a DNA molecule, the first a wire frame and the second a ball & stick view. Below are the four bases, adenine, thymine, guanine and cytosine, that are used to build this molecule. Use these bases to answer the questions in part b.

   

Four bases: adenine, cytosine, guanine and thymine

       

The colors of the atoms indicate their identity, and match those used in most molecular model sets. The one difference is that black cannot be used for carbon, as it wouldn't show up against the black background. The color key is:

H
C
N
O
Cl
F
S
white gray blue red green orange yellow