This page collects frequently asked previous year questions from Molecular Basis of Inheritance across NEET, AIIMS and CBSE boards, with worked solutions. Context: DNA structure, replication, transcription, translation and gene regulation.
Question 1 — NEET MCQ
“Which statement about molecular basis of inheritance is correct?”
Typical options test these four facts at once:
- DNA is a double helix with 10 bp per turn and 3.4 nm pitch.
- Replication is semi-conservative, discontinuous on the lagging strand.
- Eukaryotes have three RNA polymerases; prokaryotes have one.
- A deliberately wrong statement that mixes two of the above.
Usually one option contradicts a direct NCERT line. Strike it first.
Two will be subtly different versions of the same idea. Look for the unit or qualifier that separates them.
The correct answer matches the NCERT wording exactly. NEET rarely paraphrases — they quote.
Question 2 — Assertion and Reason
Assertion (A): The genetic code is triplet, degenerate and nearly universal.
Reason (R): A closely related textbook statement that may or may not explain the assertion.
Is the assertion true on its own? Verify against NCERT.
Is the reason a correct statement on its own?
This is the trick — both can be true without R being the reason for A.
Classic NEET pattern: both A and R are true, but R is not the correct explanation of A. Always check the explanation link separately.
Question 3 — match the columns
Column I lists structures or processes; Column II lists functions. A typical molecular basis of inheritance question has four or five pairs.
Usually two out of four are obvious. Lock those in and eliminate from the other column.
Even if you are unsure about the last pair, you can deduce it by exclusion.
Full marks come from method — never leave a match column blank, fill the last entry by exclusion.
Question 4 — CBSE short answer (3 marks)
“Explain the working of molecular basis of inheritance with a labelled diagram.”
A three-mark answer wants:
- 1 mark for a labelled diagram.
- 1 mark for the function statement.
- 1 mark for a mechanism sentence.
Model answer skeleton:
Molecular Basis of Inheritance is responsible for DNA structure, replication, transcription, translation and gene regulation. The key steps are: first, the input is processed; second, the intermediates form; third, the output is produced. Relevant numerical value: DNA is a double helix with 10 bp per turn and 3.4 nm pitch.
CBSE rewards crisp 3-line answers for 3 marks. Do not write an essay — you lose time and gain nothing.
Question 5 — CBSE long answer (5 marks)
A 5-mark question usually has two parts: describe the structure, then explain a disorder or application. Allocate 3 + 2 marks.
Aim for crisp diagrams over long prose. Examiners award marks for labels and sequence, not for adjectives.
For Molecular Basis of Inheritance, the repeat rate of PYQ concepts is high — around 40% of NEET questions recycle an older idea. Practise the last 10 years before touching new material.