FUT2 (Fucosyltransferase 2) is a gene that encodes an enzyme involved in synthesizing histo-blood group antigens and determining secretor status. It catalyzes the transfer of fucose to specific molecules, enabling the production of glycoproteins and glycolipids found in bodily fluids and epithelial tissues. FUT2 activity affects the expression of the H antigen — a key precursor to ABO blood group antigens — and plays a crucial role in whether these antigens are present in secretions like saliva.