only.

$(12.)q,$ is the primary information storage molecule, is a double$-$stranded, double helix and contains hereditary units called $(13.)$ It is the primary genetic material and is typically located in the $(14.)$ It's twisted ladder shape is held together by $(15.$ bonds in the "rails" or two strands and $(16.)$ bonds holding the base pairs together in the middle or "rungs." The base pairs are always $(17.)$ bonding to $(18.)$ and $(19.)$ bonding to $(20.)$

$(21.)$ is a single stranded copy of a small portion of the primary information storage molecule and moves into the $(22.)$ attaches to ribosomes and is "read" so that $(23.)q,$ can be synthesized.