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Molecular Basis of Inheritance — NEET Biology MCQs

30 questions written by hand against the NCERT chapter. Every wrong option is explained, not just the right one.

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Sample questions from this chapter

Which components must be joined to make a DNA nucleotide?
  1. Nitrogenous base, deoxyribose and phosphate ✓
  2. Amino acid, ribose and phosphate
  3. Base and sugar only
  4. Deoxyribose and peptide
Answer: A. A base attaches to 1′ carbon of deoxyribose and phosphate to 5′ carbon, forming a deoxyribonucleotide. Polynucleotides then use 3′–5′ phosphodiester bonds.
Why not B: An amino acid belongs to proteins, and ribose would identify RNA rather than DNA.
Why not C: Base plus sugar is a nucleoside; phosphate converts it to a nucleotide.
Why not D: Peptide bonds join amino acids and are absent from the nucleotide backbone.
Heavy-nitrogen bacteria are shifted to light medium. After one division, DNA forms one intermediate-density band. Which model is supported?
  1. Conservative replication with separate heavy and light bands
  2. Random mutation of nitrogen atoms
  3. Semiconservative replication producing hybrid duplexes ✓
  4. Dispersive protein synthesis
Answer: C. Every first-generation duplex contains one ¹⁵N parental strand and one ¹⁴N new strand, giving uniform intermediate density. The second generation adds a light band.
Why not A: Conservative copying predicts an intact heavy parental duplex plus a fully light daughter after one generation.
Why not B: Isotope distribution follows templated synthesis, not chemical conversion of nitrogen.
Why not D: The density measurement concerns extracted DNA, and later generations distinguish replication models.
A double-stranded DNA sample contains 20% cytosine. What percentages of guanine and adenine should it contain?
  1. G equals C, while A and T divide the remaining 60% equally ✓
  2. Guanine exceeds cytosine by 10 percentage points, leaving adenine at 20%
  3. Guanine matches cytosine at 20%, while adenine is also 20% and thymine takes the remainder
  4. The two purines, adenine and guanine, each account for 30%
Answer: A. C=G=20%, leaving 60% for A+T; therefore A=T=30%. Complementarity converts one base measurement into the full composition.
Why not B: Chargaff pairing requires G to equal C, not A.
Why not C: After 40% G+C, the remaining 60% must be shared equally by A and T.
Why not D: Purines do not equal one another individually; A pairs with T and G with C.

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Questions

How many NEET questions are there on Molecular Basis of Inheritance?

This chapter test has 30 questions — 10 easy, 14 medium and 6 hard — all written against the NCERT Class 12 chapter.

Is this NEET Biology chapter test free?

Yes. Every chapter test is free with no login, and you get your all-India rank on every one. Nothing on the site is on sale right now.

Do the questions explain the wrong options?

Yes — every distractor carries its own explanation naming the specific misconception that makes a student pick it. That is the part most question banks skip, and it is the part that changes your next attempt.