Chapter 5: Molecular Basis of Inheritance — Online MCQ Test
BIOLOGY · Grade 12 · CBSE(NCERT)
Practice Chapter 5: Molecular Basis of Inheritance with a free chapter-wise online MCQ test.
This chapter covers: DNA RNA DNA Replication Transcription Translation Genetic Code Lac Operon Human Genome Project DNA Fingerprinting Gene Regulation Chromosomes.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter 5: Molecular Basis of Inheritance — Important Questions & Answers
What is the primary function of DNA in a cell?
- A. Storage of genetic information
- B. Protein synthesis
- C. Energy production
- D. Enzyme catalysis
Answer: A. Storage of genetic information
DNA serves as the repository of genetic information that codes for all proteins and traits in an organism.
DNA serves as the repository of genetic information that codes for all proteins and traits in an organism.
Which nitrogenous bases are found in DNA?
- A. Adenine, Guanine, Cytosine, Uracil
- B. Adenine, Guanine, Cytosine, Thymine
- C. Adenine, Guanine, Uracil, Thymine
- D. Adenine, Cytosine, Uracil, Thymine
Answer: B. Adenine, Guanine, Cytosine, Thymine
DNA contains the four bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Uracil is found in RNA instead.
DNA contains the four bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Uracil is found in RNA instead.
Which of the following is NOT a step in protein synthesis?
- A. Transcription
- B. Translation
- C. Replication
- D. None - all are steps
Answer: C. Replication
Protein synthesis involves transcription (DNA to mRNA) and translation (mRNA to protein). DNA replication is a separate process for copying genetic material.
Protein synthesis involves transcription (DNA to mRNA) and translation (mRNA to protein). DNA replication is a separate process for copying genetic material.
In the genetic code, how many codons code for amino acids?
- A. 16
- B. 20
- C. 61
- D. 64
Answer: C. 61
Of the 64 possible codons (4³ combinations), 61 code for the 20 amino acids, and 3 are stop codons that terminate translation.
Of the 64 possible codons (4³ combinations), 61 code for the 20 amino acids, and 3 are stop codons that terminate translation.
A scientist observes that in a bacterial mutant, the lac operon is constitutively expressed even in the absence of lactose. Which mutation best explains this observation?
- A. Mutation in the structural genes (lacZ, lacY, lacA)
- B. Mutation in the repressor gene resulting in non-functional repressor protein
- C. Mutation in the promoter making it stronger
- D. Mutation in the CAP-binding site
Answer: B. Mutation in the repressor gene resulting in non-functional repressor protein
If the repressor protein is non-functional due to mutation, it cannot bind to the operator to block transcription, resulting in continuous expression of the lac genes regardless of lactose presence.
If the repressor protein is non-functional due to mutation, it cannot bind to the operator to block transcription, resulting in continuous expression of the lac genes regardless of lactose presence.