According to the Watson and Crick model for the structure of DNA

Question

According to the Watson and Crick model for the structure of DNA, _____ are on the outside and _____ are on the inside of the double-stranded DNA molecule, and the two strands of DNA run ____ to one another.

sugar–phosphate groups; nitrogenous bases; parallel.

nitrogenous bases; sugar–phosphate groups; parallel.

nitrogenous bases; sugar–phosphate groups; antiparallel.

nitrogenous bases; sugar–phosphate groups; haphazardly.

sugar–phosphate groups; nitrogenous bases; antiparallel.

Answer 1

The sugar-phosphate forms the so-called backbone of the DNA double helix, so they run down the outside of the linear structure. Nitrogenous bases are the components that are responsible for forming the hydrogen bonds (or base-pairing) between the two strands of DNA in the double helix, so they are on the inside. And the two strands run in opposite directions (if one goes 5' to 3', the other goes 3' to 5'), which is to say that they are "antiparallel".

Put it all together and you have your answer!