- U
- Unspecified enzyme
- UTS2
- Unspecified gene
- Unspecified receptor
- UCN
- UMOD
- USH2A
- Urea transporter
- Unspecified ligand gene
- UBE2M
- UPPS
- UPF
- UCN2
- UCP
- UBA
- UBB
- UBC
- UBD
- UBL
- UPAR
- UNC45A
- UNC13A
- USH1C
- USH1G
- UTRN
- Urease
- UNG
- UDP-Galp
- UBA1
- UBA5
- UBE2
- UBE2E2
- UBE2H
- UBE2K
- UBE2R1
- UBE3
- UROS
- Uricase
- UCK2
- UGT1A1
- UPP
- UPF1
- UCP1
- UCP2
- US28
- UV-DDB
- UBP1
- URAT1
- UBE3A
- UMPS
- UQCRB
- UCHL1
- UCHL5
- USP
- UL54
- UL97
- ULBP1
- ULBP2
- USP1
- USP2
- USP4
- USP5
- USP7
- USP8
- USP9X
- USP10
- USP11
- USP13
- USP14
- USP15
- USP19
- USP20
- USP30
- USP33
- USP21
- ULK1
- ULK2
- ULK3
- UPA