← Back to chapter
Vidaara.orgClass 12 · Mathematics
CodeVID-M12-WS
Molecular Basis of Inheritance — Practice Worksheet
Chapter: Molecular Basis of Inheritance
Topic: Molecular Basis of Inheritance
Maximum Marks: 31
Time: 30 minutes
Name: ____________________ Roll No.: __________ Date: ____________

General Instructions

  • All questions are compulsory.
  • Choose the correct option (A, B, C or D) for each question.
  • The answer key is at the end — try the paper first!
Section A — Multiple Choice (1 mark each) 17 × 1 = 17 marks
1.
The genetic material in almost all living organisms is:
  • A.Protein
  • B.DNA
  • C.Lipid
  • D.Starch
2.
The building blocks (monomers) of DNA are:
  • A.Amino acids
  • B.Nucleotides
  • C.Fatty acids
  • D.Sugars only
3.
Which sugar is present in DNA?
  • A.Ribose
  • B.Deoxyribose
  • C.Glucose
  • D.Sucrose
4.
In DNA, guanine pairs with:
  • A.Adenine
  • B.Thymine
  • C.Cytosine
  • D.Uracil
5.
The double-helix model of DNA was proposed by:
  • A.Watson and Crick
  • B.Mendel
  • C.Darwin
  • D.Pasteur
6.
Copying of DNA before cell division is called:
  • A.Translation
  • B.Replication
  • C.Transcription
  • D.Mutation
7.
DNA replication is:
  • A.Conservative
  • B.Semi-conservative
  • C.Dispersive only
  • D.Random
8.
The enzyme that builds new DNA strands is:
  • A.DNA polymerase
  • B.Amylase
  • C.Pepsin
  • D.Lipase
9.
The central dogma is:
  • A.Protein → RNA → DNA
  • B.DNA → RNA → Protein
  • C.RNA → Protein → DNA
  • D.DNA → Protein
10.
Copying a gene from DNA into mRNA is:
  • A.Translation
  • B.Transcription
  • C.Replication
  • D.Mutation
11.
In RNA, the base that replaces thymine is:
  • A.Adenine
  • B.Uracil
  • C.Cytosine
  • D.Guanine
12.
Proteins are built from mRNA at the:
  • A.Nucleus
  • B.Ribosomes
  • C.Mitochondria
  • D.Cell wall
13.
A triplet of bases coding for one amino acid is a:
  • A.Gene
  • B.Codon
  • C.Genome
  • D.Chromosome
14.
The genetic code being nearly the same in all organisms means it is:
  • A.Universal
  • B.Random
  • C.Useless
  • D.Single
15.
The complete set of an organism's DNA is its:
  • A.Genome
  • B.Codon
  • C.Allele
  • D.Ribosome
16.
The 'transforming principle' was first observed in the experiment of:
  • A.Griffith
  • B.Mendel
  • C.Darwin
  • D.Watson
17.
The lac operon of E. coli is switched on in the presence of:
  • A.Lactose
  • B.Oxygen
  • C.Sunlight
  • D.Nitrogen
Section B — Challenge / Olympiad (2 marks each) 7 × 2 = 14 marks
18.
If one DNA strand reads 5'-AATGC-3', the complementary strand reads:
  • A.TTACG
  • B.AATGC
  • C.GGCTA
  • D.UUACG
19.
Complementary base pairing is the key to accurate replication because each old strand:
  • A.Specifies the exact sequence of its new partner
  • B.Is destroyed
  • C.Makes random bases
  • D.Becomes a protein
20.
A single base change in the DNA can alter one amino acid in a protein, as in sickle-cell anaemia. This shows that:
  • A.The base sequence of a gene determines the protein
  • B.Genes are made of protein
  • C.DNA does not affect proteins
  • D.Mutations never matter
21.
The genetic code is described as 'degenerate' because:
  • A.Most amino acids are coded by more than one codon
  • B.It does not work
  • C.Each codon codes many amino acids
  • D.There are only two codons
22.
DNA fingerprinting can identify individuals because each person (except identical twins) has a:
  • A.Unique pattern in their DNA
  • B.Different number of cells
  • C.Different blood only
  • D.Identical genome
23.
The near-universality of the genetic code across bacteria, plants and humans is strong evidence that all life:
  • A.Shares a common origin
  • B.Evolved separately
  • C.Has no DNA
  • D.Uses different codes
24.
The lac operon staying OFF when no lactose is present benefits the cell by:
  • A.Saving energy by not making unneeded enzymes
  • B.Killing the cell
  • C.Making more DNA
  • D.Stopping all genes

Answer Key

Section A — Multiple Choice (1 mark each)
  1. (B) DNA
  2. (B) Nucleotides
  3. (B) Deoxyribose
  4. (C) Cytosine
  5. (A) Watson and Crick
  6. (B) Replication
  7. (B) Semi-conservative
  8. (A) DNA polymerase
  9. (B) DNA → RNA → Protein
  10. (B) Transcription
  11. (B) Uracil
  12. (B) Ribosomes
  13. (B) Codon
  14. (A) Universal
  15. (A) Genome
  16. (A) Griffith
  17. (A) Lactose
Section B — Challenge / Olympiad (2 marks each)
  1. (A) TTACG
  2. (A) Specifies the exact sequence of its new partner
  3. (A) The base sequence of a gene determines the protein
  4. (A) Most amino acids are coded by more than one codon
  5. (A) Unique pattern in their DNA
  6. (A) Shares a common origin
  7. (A) Saving energy by not making unneeded enzymes
Generated by Vidaara.org · Assignment VID-M12-WS · vidaara.org