minor groove

ma·jor groove

in a detailed analysis of DNA structure, there are two types of grooves that can be seen; the major groove has the nitrogen and oxygen atoms of the base pairs pointing inward toward the helical axis, whereas in the minor groove, the nitrogen and oxygen atoms point outwards; important because the major groove is more dependent on base composition and may be the site for protein recognition of specific DNA sequences or regions.

minor groove

A shallow “furrow” in the molecular structure of a DNA double helix, which measures 1.2 nm across and extends the entire length of DNA as long as the molecule remains in a normal or right-handed DNA conformation.