Class 12 Biology MCQ Chapter 6 Molecular Basis of Inheritance
Master the science behind genes and heredity with our Class 12 Biology MCQ Chapter 6 Molecular Basis of Inheritance English Medium collection. This article includes a comprehensive set of multiple-choice questions (MCQs) with answers, specially prepared for AHSEC Higher Secondary students to support effective revision and exam preparation.
The chapter Molecular Basis of Inheritance explains how genetic information is stored, transmitted, and expressed in living organisms. Students will study important topics such as DNA structure, RNA, replication, transcription, translation, genetic code, gene expression, mutations, and the contributions of famous scientists to molecular genetics. These concepts are essential for understanding modern biology and are frequently featured in board examinations.
All MCQs are developed according to the latest AHSEC syllabus and examination pattern, making them highly useful for self-assessment and concept building. Regular practice of these objective questions will help students improve their understanding of molecular genetics, enhance problem-solving skills, and gain confidence in answering Biology questions accurately.
Whether you are revising key topics or preparing for the AHSEC Higher Secondary Final Examination, these Chapter 6 MCQ solutions will help you strengthen your knowledge and achieve better results in Biology.
Unit VII: Genetics and Evolution
Molecular Basis of Inheritance
VSA & MCQ
I. Very Short Question-Answers
Q. Who proposed the double helix model of DNA?
Ans: James Watson and Francis Crick.
Q. What is DNA?
Ans: DNA is deoxyribonucleic acid, the hereditary material in most organisms.
Q. What is the full form of RNA?
Ans: Ribonucleic acid.
Q. What is a nucleotide?
Ans: A nucleotide is the basic unit of nucleic acids.
Q. Name the sugar present in DNA.
Ans: Deoxyribose sugar.
Q. Name the nitrogenous bases present in DNA.
Ans: Adenine, thymine, guanine and cytosine.
Q. Which nitrogenous base is absent in DNA but present in RNA?
Ans: Uracil.
Q. What is a gene?
Ans: A gene is a segment of DNA that controls a specific character.
Q. What are complementary base pairs in DNA?
Ans: Adenine pairs with thymine and guanine pairs with cytosine.
Q. State Chargaff’s rule.
Ans: In DNA, A = T and G = C.
Q. What type of bond joins complementary bases in DNA?
Ans: Hydrogen bond.
Q. What is DNA replication?
Ans: DNA replication is the process of formation of identical DNA molecules.
Q. What is semiconservative replication?
Ans: Each new DNA molecule contains one parental strand and one newly synthesized strand.
Q. Who proved semiconservative replication of DNA?
Ans: Matthew Meselson and Franklin Stahl.
Q. What is transcription?
Ans: Transcription is the process of synthesis of RNA from DNA.
Q. What is translation?
Ans: Translation is the process of protein synthesis from mRNA.
Q. What is mRNA?
Ans: Messenger RNA carries genetic information from DNA to ribosome.
Q. What is tRNA?
Ans: Transfer RNA carries amino acids to ribosome during protein synthesis.
Q. What is rRNA?
Ans: Ribosomal RNA forms structural and functional part of ribosomes.
Q. What is codon?
Ans: A codon is a sequence of three nucleotides coding for one amino acid.
Q. What is anticodon?
Ans: Anticodon is a sequence of three nucleotides on tRNA complementary to codon.
Q. How many codons code for amino acids?
Ans: 61 codons.
Q. Name the start codon.
Ans: AUG.
Q. Name the stop codons.
Ans: UAA, UAG and UGA.
Q. What is the genetic code?
Ans: Genetic code is the sequence of codons that determines amino acid sequence.
Q. What is mutation?
Ans: Mutation is a sudden heritable change in genetic material.
Q. What is the Human Genome Project?
Ans: It is an international project to identify all genes in human DNA.
Q. What is biotechnology?
Ans: Biotechnology is the use of living organisms or their products for human welfare.
Q. What is lac operon?
Ans: Lac operon is a group of genes regulating lactose metabolism in bacteria.
Q. Name the enzyme responsible for DNA replication.
Ans: DNA polymerase.
II. Multiple Choice Questions (MCQs)
Q. The hereditary material in most organisms is:
(a) Protein
(b) Lipid
(c) DNA
(d) Carbohydrate
Ans: (c) DNA
Q. DNA stands for:
(a) Deoxyribose nucleic acid
(b) Deoxyribonucleic acid
(c) Double ribose nucleic acid
(d) Dinucleic acid
Ans: (b) Deoxyribonucleic acid
Q. The sugar present in DNA is:
(a) Ribose
(b) Glucose
(c) Deoxyribose
(d) Fructose
Ans: (c) Deoxyribose
Q. Which nitrogenous base is present only in RNA?
(a) Adenine
(b) Cytosine
(c) Guanine
(d) Uracil
Ans: (d) Uracil
Q. Complementary base pairing in DNA is:
(a) A–G and T–C
(b) A–T and G–C
(c) A–C and G–T
(d) A–U and G–C
Ans: (b) A–T and G–C
Q. The double helix model of DNA was proposed by:
(a) Mendel and Morgan
(b) Darwin and Lamarck
(c) Watson and Crick
(d) Meselson and Stahl
Ans: (c) Watson and Crick
Q. The bond between complementary bases is:
(a) Ionic bond
(b) Hydrogen bond
(c) Peptide bond
(d) Glycosidic bond
Ans: (b) Hydrogen bond
Q. According to Chargaff’s rule:
(a) A = G
(b) T = C
(c) A = T
(d) G = T
Ans: (c) A = T
Q. DNA replication is:
(a) Conservative
(b) Dispersive
(c) Semiconservative
(d) Non-conservative
Ans: (c) Semiconservative
Q. Semiconservative replication was proved by:
(a) Watson and Crick
(b) Meselson and Stahl
(c) Mendel and Morgan
(d) Hershey and Chase
Ans: (b) Meselson and Stahl
Q. RNA synthesis from DNA is called:
(a) Translation
(b) Replication
(c) Mutation
(d) Transcription
Ans: (d) Transcription
Q. Protein synthesis occurs during:
(a) Replication
(b) Mutation
(c) Translation
(d) Transcription
Ans: (c) Translation
Q. mRNA carries information from:
(a) Ribosome to DNA
(b) DNA to ribosome
(c) Cytoplasm to nucleus
(d) tRNA to ribosome
Ans: (b) DNA to ribosome
Q. The adaptor molecule in protein synthesis is:
(a) mRNA
(b) rRNA
(c) tRNA
(d) DNA
Ans: (c) tRNA
Q. Ribosomes are mainly made of:
(a) DNA and protein
(b) RNA and protein
(c) Lipid and RNA
(d) Carbohydrate and protein
Ans: (b) RNA and protein
Q. A codon consists of:
(a) One nucleotide
(b) Two nucleotides
(c) Three nucleotides
(d) Four nucleotides
Ans: (c) Three nucleotides
Q. The start codon is:
(a) UAA
(b) AUG
(c) UGA
(d) UAG
Ans: (b) AUG
Q. Which one is a stop codon?
(a) AUG
(b) GUG
(c) UAA
(d) AAG
Ans: (c) UAA
Q. Total number of codons in genetic code is:
(a) 20
(b) 61
(c) 64
(d) 66
Ans: (c) 64
Q. Amino acids are coded by:
(a) 20 codons
(b) 61 codons
(c) 64 codons
(d) 3 codons
Ans: (b) 61 codons
Q. Mutation means:
(a) Normal growth
(b) Sudden heritable change
(c) Cell division
(d) Protein synthesis
Ans: (b) Sudden heritable change
Q. The enzyme involved in DNA replication is:
(a) RNA polymerase
(b) DNA polymerase
(c) Ligase only
(d) Amylase
Ans: (b) DNA polymerase
Q. Human Genome Project aimed to:
(a) Clone humans
(b) Sequence human DNA
(c) Produce vaccines
(d) Study fossils
Ans: (b) Sequence human DNA
Q. The functional unit of inheritance is:
(a) Chromosome
(b) Ribosome
(c) Gene
(d) Centromere
Ans: (c) Gene
Q. RNA differs from DNA because RNA contains:
(a) Thymine
(b) Deoxyribose
(c) Uracil
(d) Histone
Ans: (c) Uracil
Q. The process of copying DNA into RNA is:
(a) Translation
(b) Mutation
(c) Replication
(d) Transcription
Ans: (d) Transcription
Q. Lac operon is related to:
(a) Protein digestion
(b) Lactose metabolism
(c) Fat synthesis
(d) DNA repair
Ans: (b) Lactose metabolism
Q. Which RNA carries amino acids to ribosome?
(a) mRNA
(b) rRNA
(c) tRNA
(d) hnRNA
Ans: (c) tRNA
Q. The sequence of bases in mRNA is read in groups of:
(a) One
(b) Two
(c) Three
(d) Four
Ans: (c) Three
Q. The process of formation of identical DNA copies is called:
(a) Translation
(b) Replication
(c) Mutation
(d) Transcription
Ans: (b) Replication
Q. Assertion (A): DNA replication is semiconservative.
Reason (R): Each daughter DNA molecule contains one parental strand and one newly formed strand.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (b)
Q. Assertion (A): AUG is the initiation codon.
Reason (R): AUG codes for methionine amino acid.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
Q. Assertion (A): RNA contains thymine.
Reason (R): RNA contains uracil instead of thymine.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (d)
Q. Assertion (A): tRNA is called adaptor molecule.
Reason (R): tRNA carries amino acids to ribosome during translation.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
Q. Assertion (A): Mutation produces genetic variation.
Reason (R): Mutation is a sudden heritable change in DNA.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (b)
Q. Assertion (A): Lac operon regulates lactose metabolism in bacteria.
Reason (R): Lac operon contains structural and regulatory genes.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (c)
Q. Assertion (A): Complementary bases in DNA are joined by hydrogen bonds.
Reason (R): Adenine pairs with cytosine and guanine pairs with thymine.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (c)
