Which of these is used as a tracking dye in SDS PAGE of protein
(a) Bromo phenol blue
(b) Xylene cyanol
(c) Orange G
(d) All of the above

The correct answer is:

(d) All of the above

Explanation:

In SDS-PAGE (Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis), tracking dyes are used to monitor the progress of electrophoresis and ensure proper migration of proteins. Different dyes migrate at different speeds, allowing flexibility based on experimental needs.

1. Bromophenol Blue (BPB) → Most commonly used tracking dye. It migrates faster than most proteins.
2. Xylene Cyanol → Moves slower than bromophenol blue and is useful for tracking larger proteins.
3. Orange G → Moves faster than bromophenol blue and is sometimes used when tracking smaller peptides or when alternative dyes are needed.

Since all three dyes can be used as tracking dyes in SDS-PAGE, the correct answer is:
(d) All of the above ✅