1. Count the number of nucleotides present in the DNA molecule: _ nucleotides. 2. The location of a hydrogen bond.

3. Identify the bases that pair together.

_ and _

_ and _

4. Describe two reasons why the image you chose shows a double helix.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.