What is the meaning of proactive

Pretty much just acting before something happens. Acting in anticipation of something before it happens without being asked. Something like that-

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: