DNA Structure Activity

Problem 9: Location of GC and AT base pairs in DNA double helix

You have just created a view that shows only the bases of the A-T and G-C base pairs . How are the bases oriented in the DNA structure? The planar bases:

A.	stack on top of each other, perpendicular to the helix axis The base pairs are planar, and stack atop one another in the interior of the double helix, perpendicular to the helix axis.
B.	stack on top of each other, parallel to the helix axis
C.	do not stack on top of each other