The GATE Grind

GATE 2019 BT – Question 43

Recombinant DNA Technology and Other Tools in Biotechnology · Analytical tools: Electrophoresis, microarrays, enzymatic assays, immunoassays, immunoblotting, flow cytometry, whole genome and ChIP sequencing · 2 marks · Multiple choice

Hexapeptide P has pI 6.9. Variant Q replaces glutamate at position 3 with valine. They undergo polyacrylamide-gel electrophoresis at pH 8.0. Which is CORRECT?

  1. P migrates faster than Q toward the anode.
  2. P migrates faster than Q toward the cathode.
  3. They migrate together.
  4. Q migrates faster than P toward the anode.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) P migrates faster than Q toward the anode.

Explanation

At pH above its pI, P is negatively charged and moves toward the positive anode. Removing a glutamate carboxylate in Q makes Q less negative under these conditions. With comparable hexapeptide sizes, P therefore has the larger anodal mobility, A. This is the charge-dependent native electrophoresis interpretation, not SDS-imposed equal charge-to-mass migration.

More Analytical tools: Electrophoresis, microarrays, enzymatic assays, immunoassays, immunoblotting, flow cytometry, whole genome and ChIP sequencing questions

All Analytical tools: Electrophoresis, microarrays, enzymatic assays, immunoassays, immunoblotting, flow cytometry, whole genome and ChIP sequencing questions →