Practice Questions

One complete helical turn spans a longitudinal length of 3.4 nm (34 A˚) and contains approximately 10 base pairs.

Chargaff’s rules dictate that [A]=[T] and [G]=[C]; therefore, the sum of purines (A+G) must equal the sum of pyrimidines (T+C).

Rosalind Franklin’s famous "Photo 51" obtained via X-ray crystallography revealed the helical configuration and dimensions of the DNA molecule.

Phosphodiester bonds covalently link the 3' carbon of one deoxyribose sugar to the 5' carbon of the adjacent sugar via a phosphate group.

The double helix maintains a constant width of 2 nm (20 A˚) because a double-ringed purine always pairs with a single-ringed pyrimidine.

Adenine (a purine) always pairs with thymine (a pyrimidine) using two hydrogen bonds in standard Watson-Crick base pairing.

The 5' end of a DNA or RNA strand terminates in a phosphate group attached to the 5' carbon of the pentose sugar.

A gene is the fundamental structural and functional unit of heredity, consisting of a nucleotide sequence that carries the code for a protein.

Guanine pairs with cytosine via three hydrogen bonds, creating a more thermally stable bond than the adenine-thymine pair.

One strand runs in the 5' to 3' direction while its complementary partner runs in the 3' to 5' direction.