Biology Reference
In-Depth Information
Figure 1.7
A) Complementary base pairing of polynucleotides by hydrogen bonds holds the two
strands of the DNA molecule together. B) Thymine (T) pairs with adenine (A) with two hydrogen
bonds, and guanine (G) pairs with cytosine (C) with three hydrogen bonds.
In addition, C-, D-, E-, and Z-DNA have been found. Z-DNA has a left-handed
helix rather than a right-handed helix. A triple-helical form (H-DNA) also occurs.
A, H, and Z forms of DNA are thought to occur in cells, and C, D, and E forms of
DNA may be produced only under laboratory conditions.
