The chapter Molecular Basis of Inheritance is one of the most scoring yet concept-heavy units in NEET Biology. Questions are directly picked from NCERT lines, diagrams, and processes like DNA replication, transcription, translation, and operon regulation. If your concepts are sharp, this chapter can easily fetch you full marks. This guide on Top 5 Molecular Basis Questions is designed to give you dense, high-yield revision with the most repeated PYQs and clear conceptual explanations.
If you want to improve accuracy and speed, mastering these Top 5 Molecular Basis Questions is non-negotiable.
Why Molecular Basis is High Weightage in NEET
The Molecular Basis chapter builds the foundation of modern genetics. NEET consistently asks direct and concept-based questions from:
- DNA structure and replication
- RNA types and transcription
- Protein synthesis (translation)
- Lac operon and gene regulation
A strong command over NCERT diagrams and terminology is essential to crack Top 5 Molecular Basis Questions effectively.
Top 5 Molecular Basis Questions (Most Repeated PYQs with Concepts)
Question 1: DNA replication is semi-conservative. What does this mean?
Options:
A. DNA is completely new
B. One strand is old, one is new
C. Both strands are old
D. DNA is randomly formed
Correct Answer: B. One strand is old, one is new
Explanation:
Semi-conservative replication means each daughter DNA molecule contains one parental strand and one newly synthesized strand. This was experimentally proven by Meselson and Stahl using isotopes of nitrogen. During replication, DNA unwinds, and each strand acts as a template for the formation of a new complementary strand.
This concept is repeatedly tested in Top 5 Molecular Basis Questions, especially through experimental-based MCQs.
Question 2: Which enzyme synthesizes DNA during replication?
Options:
A. Helicase
B. DNA polymerase
C. Ligase
D. Primase
Correct Answer: B. DNA polymerase
Explanation:
DNA polymerase catalyzes the addition of nucleotides to the growing DNA strand in the 5′ → 3′ direction. It requires a primer and cannot initiate synthesis on its own. Helicase unwinds DNA, ligase joins Okazaki fragments, and primase synthesizes RNA primers.
Understanding enzyme functions is crucial for solving Top 5 Molecular Basis Questions accurately.
Question 3: Which RNA type carries amino acids to the ribosome?
Options:
A. mRNA
B. rRNA
C. tRNA
D. snRNA
Correct Answer: C. tRNA
Explanation:
Transfer RNA (tRNA) carries specific amino acids to the ribosome during translation. Each tRNA has an anticodon that pairs with the codon on mRNA, ensuring correct amino acid placement in the growing polypeptide chain.
Such structure-function questions are very common in Top 5 Molecular Basis Questions.
Question 4: What is the function of the lac operon?
Options:
A. DNA repair
B. Lactose metabolism
C. Protein folding
D. Cell division
Correct Answer: B. Lactose metabolism
Explanation:
The lac operon is an inducible operon present in bacteria like E. coli. It regulates genes responsible for lactose metabolism. In the absence of lactose, the repressor binds to the operator, preventing transcription. When lactose is present, it acts as an inducer, removing the repressor and allowing gene expression.
This is one of the highest-weightage topics in Top 5 Molecular Basis Questions.
Question 5: Which codon acts as a start signal in translation?
Options:
A. UAA
B. UAG
C. AUG
D. UGA
Correct Answer: C. AUG
Explanation:
AUG is the start codon and codes for methionine. It signals the beginning of protein synthesis. UAA, UAG, and UGA are stop codons that terminate translation.
Codon-based questions are frequently asked in Top 5 Molecular Basis Questions, especially direct NCERT lines.
High-Yield Concept Summary (Dense Revision)
To master Top 5 Molecular Basis Questions, you must clearly understand the following:
DNA is a double helix composed of two antiparallel strands held together by hydrogen bonds between complementary bases (A-T, G-C). Replication is semi-conservative, bidirectional, and semi-discontinuous. The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments called Okazaki fragments, later joined by ligase.
Transcription is the process of RNA synthesis from DNA, carried out by RNA polymerase. The coding strand has the same sequence as mRNA (except T → U), while the template strand is used for synthesis. Translation occurs in ribosomes, where mRNA codons are read, and tRNA brings amino acids to form polypeptides.
The genetic code is triplet, degenerate, and universal. AUG acts as the start codon, while UAA, UAG, and UGA are stop codons. The lac operon demonstrates gene regulation and is a classic example of inducible gene expression.
This dense conceptual clarity is essential for solving Top 5 Molecular Basis Questions quickly and accurately.
Additional Practice Questions (Concept-Based Rapid Revision)
Strengthen your preparation for Top 5 Molecular Basis Questions with these rapid revision problems:
1. Which bond links nucleotides in DNA?
Answer: Phosphodiester bond
2. Which enzyme removes RNA primers?
Answer: DNA polymerase I
3. What is the role of helicase?
Answer: Unwinds DNA
4. Which RNA forms ribosomes?
Answer: rRNA
5. What is the function of ligase?
Answer: Joins Okazaki fragments
6. Which strand is synthesized continuously?
Answer: Leading strand
7. What is an anticodon?
Answer: Triplet on tRNA complementary to mRNA codon
8. Where does translation occur?
Answer: Ribosome
9. What is the genetic material in viruses (some)?
Answer: RNA
10. Which operon is inducible?
Answer: Lac operon
Smart Strategy to Master This Chapter
To excel in Top 5 Molecular Basis Questions, follow a focused approach. Read NCERT line-by-line and revise diagrams multiple times. Pay special attention to enzyme names, directions (5′ → 3′), and codon tables. Practice PYQs regularly and revise conceptual summaries instead of rote learning.
Repeated revision of Top 5 Molecular Basis Questions ensures better retention and fewer mistakes.
Common Mistakes to Avoid
Many students lose marks in Top 5 Molecular Basis Questions due to confusion between enzymes like helicase and polymerase, misunderstanding codons and anticodons, ignoring operon regulation, and not revising diagrams properly. Avoiding these mistakes can significantly improve your score.
Conclusion
This dense guide on Top 5 Molecular Basis Questions provides the most important NEET PYQs along with clear explanations and rapid revision. Since this chapter is heavily NCERT-based and high scoring, mastering it can give you a strong edge in NEET Biology.
With consistent practice and revision, Top 5 Molecular Basis Questions can become one of your most reliable scoring areas.
FAQs
Q1. How many questions come from Molecular Basis in NEET?
Usually 2–4 questions are asked every year.
Q2. Is NCERT enough for this chapter?
Yes, NCERT is sufficient for Top 5 Molecular Basis Questions.
Q3. Which topic is most important?
DNA replication, transcription, and lac operon are highly important.
Q4. How to revise quickly?
Focus on diagrams, enzyme functions, and PYQs like these Top 5 Molecular Basis Questions.