Hey Gattaca,
Is this from the movie, Gattaca. I'd had my "home email account" start with Gattaca (if you check my profile) since 1997, the year the movie came out. When I saw the film, I knew there was some significance with that wordchoice, 9th grade biology memories. I wasn't any good at genetics so we learned that g.a.t.t. was a clue to remember the bases of DNA.
From: IMBD.com
"The name "Gattaca" is composed entirely of the letters used to label the nucleotide bases of DNA. The four nucleotode bases of DNA (deoxyribonucleic acid) are adenine, thymine, cytosine, and guanine."