Measuring a size distribution of nucleic acid molecules in a sample

A process for measuring a size distribution of a plurality of nucleic acid molecules, the process comprising:

• labeling the nucleic acid molecules with a fluorescent dye comprising a plurality of fluorescent dye molecules to form labeled nucleic acid molecules, such that a number of fluorescent dyes molecules attached to each nucleic acid molecule is reliably proportional to the number of base pairs in the nucleic acid molecule for nucleic acid molecules consisting of 10 base pairs to 50 base pairs, and the fluorescent dye molecules having a first florescence spectrum;
• producing, by the labeled nucleic acid molecules, the first florescence spectrum in response to irradiating the labeled nucleic acid molecules at the first wavelength;
• and
• detecting the first florescence spectrum to measure the size distribution of the plurality of nucleic acid molecules for nucleic acid molecules consisting of 10 base pairs to 50 base pairs;
• and
• determining a size of single nucleic acid molecules in the labeled nucleic acid molecules, based on a quantitative calibration of the first fluorescence spectrum detected and nucleic acid molecule size in terms of a number of base pairs.