Thi nghiem Griffith, đuoc Frederick Griffith bao cao vao nam 1928, la thi nghiem đau tien chung to vi khuan co kha nang truyen thong tin di truyen thong qua qua trinh bien nap. Ket qua cua Griffith đuoc nghien cuu mo rong vao cuoi thap nien 1930 va đau thap nien 1940 voi ket qua co lap đuoc DNA va chung to no la phan tu mang thong tin di truyen.
Viem phoi la can benh gay tu vong lon trong đai dich cum Tay Ban Nha luc hau chien tranh the gioi lan I, va Frederick Griffith luc nay đang nghien cuu kha nang nham tim ra loai vac-xin phong benh. Griffith su dung hai chung phe cau khuan (Streptococcus pneumoniae) gay nhiem o chuot – chung vi khuan loai III-S (chung bo nhan smooth) gay đoc, va chung loai II-R (chung bo nham rough) trung tinh khong đoc. Chung III-S tong hop mot lop vo nhay polysaccharide bao ve chung khoi he mien dich cua sinh vat chu, khien vat chu bi chet, trong khi chung II-R khong co lop vo bao ve nay va he thong mien dich cua sinh vat chu co the ngan chan đuoc. Nha vi khuan hoc nguoi Đuc, Fred Neufeld, đa kham pha ra ba loai phe cau khuan (loai I, II, va III) đong thoi kham pha ra phan ung Quellung đe nhan dien chung trong ong nghiem (in vitro). Cho đen khi Griffith bao cao ket qua thi nghiem, cac nha vi khuan hoc tin tuong rang cac chung vi khuan la co đinh va khong the thay đoi đuoc, tu the he nay sang the he khac.
Trong thi nghiem, ong dung nhiet tieu diet chung vi khuan III-S, va su dung ky thuat loc đe tron xac cua chung voi chung vi khuan II-R. Khi cho chuot nhiem chi rieng chung II-R thi chung van song binh thuong, trong khi cho nhiem hon hop dung dich chua xac chung vi khuan III-S va vi khuan song II-R thi chuot bi benh va chet. Griffith sau đo con tach loc đuoc vi khuan con song co ca chung phe cau khuan II-R va III-S tu mau cua nhung con chuot đa chet. Griffith ket luan rang chung II-R đa "bien đoi" sang chung gay đoc III-S boi "chat bien nap chu yeu" (transforming principle) dua tren nhung phan nao đo tu xac cua chung III-S.
Ngay nay chung ta biet rang "chat bien nap" ma Griffith đa quan sat thay chinh la DNA cua chung vi khuan III-S. Trong khi chung nay đa bi diet boi nhiet, cac phan tu DNA cua chung van ton tai tu qua trinh xu ly nhiet va đuoc tiep nhan boi vi khuan chung II-R. DNA cua chung III-S chua cac gene ma hoa cho lop mang nhay polysaccharide giup bao ve vi khuan. Đuoc trang bi cac gene nay, cac the he tiep theo cua chung vi khuan II-R chong lai đuoc he mien dich cua chuot va dan toi cai chet cua sinh vat chu. Ban chat chinh xac cua chat bien nap chu yeu (DNA) đuoc xac nhan bang thuc nghiem boi cac nha sinh hoc Avery, McLeod va McCarty va bang thi nghiem thuc hien boi Hershey va Chase.


Chu thich Tham khao Avery, MacLeod, and McCarty (1944). "Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III". Journal of Experimental Medicine. Quyen 79 so 1. tr. 137–158. doi:10.1084/jem.79.2.137. PMC 2135445. PMID 19871359.{{Chu thich tap chi}}:  Quan ly CS1: nhieu ten: danh sach tac gia (lien ket)
(References the original experiment by Griffith. Original article Luu tru ngay 29 thang 6 nam 2008 tai Wayback Machine and 35th anniversary reprint available.)


Đoc them Daniel Hartl; Elizabeth Jones (2005). Genetics: Analysis of Genes and Genomes, 6th edition. Jones & Bartlett. 854 pages. ISBN 0-7637-1511-5.
Lehrer, Steven (2006). Explorers of the Body (an ban thu 2). United States: iUniverse, Inc. ISBN 0-595-40731-5.