An oligonucleotide bound to a protein migrates slower than the free oligonucleotide in a polyacrylamide gel. If
antibody specific to the oligonucleotide binding protein is bound to this complex, the antibody treated complex
will

a. Migrate slower than both the free oligonucleotide and the untreated complex.
b. Migrate slower than the free oligonucleotide but faster than the untreated complex
c. Migrate at the same rate as the untreated complex
d. Migrate at the same rate as the free oligonucleotide

The correct answer is:

✅ (a) Migrate slower than both the free oligonucleotide and the untreated complex.

Explanation:

In polyacrylamide gel electrophoresis (PAGE), molecules migrate based on size and charge.

1. Free oligonucleotide

   • Small and negatively charged → Moves fastest through the gel.

2. Oligonucleotide + Protein Complex

   • When a protein binds to the oligonucleotide, it increases the molecular weight and alters charge distribution, making the complex migrate slower than the free oligonucleotide.

3. Oligonucleotide + Protein Complex + Antibody

   • When an antibody binds to the protein-oligonucleotide complex, the complex size further increases.
   • Larger complexes experience more resistance in the gel matrix, causing them to migrate even slower than the untreated complex.

Why Not the Other Options?

• (b) Migrate slower than the free oligonucleotide but faster than the untreated complex ❌ → Incorrect, because the antibody increases the molecular weight, further reducing mobility.
• (c) Migrate at the same rate as the untreated complex ❌ → Incorrect, because adding the antibody increases size, slowing migration.
• (d) Migrate at the same rate as the free oligonucleotide ❌ → Incorrect, because both protein binding and antibody addition increase molecular size, slowing migration.

Conclusion:

Since the antibody increases the complex’s molecular weight, it will migrate even slower than the untreated complex and the free oligonucleotide.

✅ Correct answer: (a) Migrate slower than both the free oligonucleotide and the untreated complex.