miRNA seed types. Nine seed types are categorized in two groups; "Stringent" (8mer, 7mer-A1, and 7mer-m8) and "Non-stringent" (6mer, GUM, GUT, LP, BM and BT). GUM and GUT allow one GU wobble in the seed region. GUM has the U on miRNA whereas GUT has the U on the target. LP, BM and BT allow one mismatch. LP has one loop, BM has one bulge on miRNA, and BT has one bulge on the target.