Molecular Basis of Inheritance — Class 12 Biology NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 12 Biology chapter "Molecular Basis of Inheritance" — 7 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 12 Biology chapter "Molecular Basis of Inheritance" — 7 important questions with detailed answers for CBSE…

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

What is DNA? Describe the structure of DNA with a labeled diagram description.
Describe DNA replication and the role of DNA polymerase. What is semi-conserv…
What is the central dogma of molecular biology? Explain the process of transc…
What is the genetic code? Explain its characteristics and significance.
Describe the process of translation. Explain the role of tRNA and ribosome.
What is protein synthesis? Explain the synthesis of a specific protein starti…
+ 1 more questions in the full chapter

Solutions Summary:

Question	Status
What is DNA? Describe the structure of DNA with a labeled…	✓ Solved
Describe DNA replication and the role of DNA polymerase. …	✓ Solved
What is the central dogma of molecular biology? Explain t…	✓ Solved
What is the genetic code? Explain its characteristics and…	✓ Solved
Describe the process of translation. Explain the role of …	✓ Solved
What is protein synthesis? Explain the synthesis of a spe…	✓ Solved

Showing 6 of 7 questions

Q1: What is DNA? Describe the structure of DNA with a labeled diagram description.

DNA (Deoxyribonucleic acid): Macromolecule carrying genetic information for all living organisms. Double helix polymer of nucleotides. Structure (Watson-Crick model): 1. Basic units (Nucleotides): Each contains three components: - Nitrogenous base: Purines (Adenine-A, Guanine-G) or Pyrimidines (Cytosine-C, Thymine-T) - Pentose sugar: Deoxyribose (5-carbon sugar, lacks hydroxyl at 2' carbon unlike RNA) - Phosphate group: Links nucleotides 2. Primary structure (Backbone): - Sugar-ph...

Q2: Describe DNA replication and the role of DNA polymerase. What is semi-conservative replication?

DNA Replication: Process of exact duplication of DNA molecule, occurring during S phase of cell cycle. Produces two identical DNA molecules from one. Semi-conservative replication (Meselson-Stahl experiment): - Definition: Each new DNA molecule contains one original strand and one newly synthesized strand - Mechanism: Original double helix separates; each strand serves as template for new complementary strand - Result: Two daughter molecules, each 50% old (parental) DNA and 50% new DNA Process...

Q3: What is the central dogma of molecular biology? Explain the process of transcription.

Central Dogma: Fundamental principle stating genetic information flows from DNA to RNA to Protein. Information in DNA transferred to RNA, which directs protein synthesis. Unidirectional for most organisms (exception: reverse transcriptase in retroviruses). Flow: DNA → RNA (transcription) → Protein (translation) Transcription: Process synthesizing RNA from DNA template. Occurs in nucleus (eukaryotes) or cytoplasm (prokaryotes). Types of RNA produced: - mRNA (messenger RNA): carries genetic inf...

Q4: What is the genetic code? Explain its characteristics and significance.

Genetic code: Sequence of bases in DNA/mRNA specifying amino acid sequence in proteins. Language translating genetic information into protein structure. Characteristics of genetic code: 1. Triplet code: - Three consecutive nucleotides (codon) code for one amino acid - 64 possible codons (4^3 combinations of 4 bases) - 61 codons code for amino acids; 3 stop codons 2. Universal code: - Same codons represent same amino acids across all organisms - Evidence: bacteria and humans sha...

Q5: Describe the process of translation. Explain the role of tRNA and ribosome.

Translation: Process synthesizing proteins from mRNA template. Converts genetic information in nucleic acids to amino acid sequence in proteins. Stages of translation (in prokaryotes): 1. Initiation: - mRNA binds to small ribosomal subunit (30S in prokaryotes, 40S in eukaryotes) - Shine-Dalgarno sequence in prokaryotes positions mRNA correctly - Initiator tRNA (fMet-tRNA in prokaryotes, Met-tRNA in eukaryotes) binds to start codon (AUG) - Large ribosomal subunit (50S prokaryotes, 6...

Q6: What is protein synthesis? Explain the synthesis of a specific protein starting from DNA to final protein.

Protein synthesis: Overall process of producing functional proteins from genetic information stored in DNA. Two-stage process: transcription and translation. Complete pathway from DNA to functional protein: 1. Gene selection: - Specific gene on DNA selected for expression - Gene contains: * Regulatory sequences: promoter, enhancer, silencer * Exons: coding sequences (in eukaryotes) * Introns: non-coding sequences (in eukaryotes) 2. Transcription: - RNA polymerase binds...

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