Question

Which of the following is desirable in a primer for PCR?

• A. Should always be more than 50 nucleotides in length
• B. Secondary structures such as hairpins
• C. Sequences with stretches of identical single nucleotides
• D. Minimal complementarity between reverse and forward primers

Hint:

Good primers: - 18–25 bases - No hairpins - No repeats - No complementarity between primers

Answer 1

The Correct Option is D

Concept: PCR primers must be designed carefully to ensure efficient and specific amplification.

Step 1: Ideal primer characteristics.

• Length: typically 18--25 nucleotides
• No secondary structures (like hairpins)
• No long stretches of identical bases
• Minimal complementarity between primers (to avoid primer-dimers)

Step 2: Analyze options.

• (A) Incorrect → Too long (not ideal)
• (B) Incorrect → Hairpins reduce efficiency
• (C) Incorrect → Repeats cause mispriming
• (D) Correct → Prevents primer-dimer formation

Step 3: Final conclusion.
Thus, the desirable feature is: \[ Minimal complementarity between forward and reverse primers \]