Exhibit 8.1 [LETTERHEAD OF LATHAM & WATKINS] December 13, 2002 Hyseq, Inc. 670 Alamanor Avenue Sunnyvale, California 94085 RE: AGREEMENT AND PLAN OF MERGER BY AND AMONG HYSEQ, INC., VERTICAL MERGER CORP., AND VARIAGENICS, INC. DATED AS OF NOVEMBER 9,...Hyseq Inc • December 13th, 2002 • In vitro & in vivo diagnostic substances
