Top 20 MCQs on DNA, Genes & Genetics – Biology GK for Competitive Exams

  1. What is the full form of DNA?
    a) Deoxyribonucleic acid
    b) Deoxyribogenetic acid
    c) Deoxyribonitric acid
    d) Deoxyriboneuro acid
    Answer: a) Deoxyribonucleic acid
  2. Where is the DNA located in a cell?
    a) Cytoplasm
    b) Cell wall
    c) Nucleus
    d) Mitochondria
    Answer: c) Nucleus
  3. Which of the following is not a nitrogenous base of DNA?
    a) Thymine
    b) Cytosine
    c) Uracil
    d) Adenine
    Answer: c) Uracil
  4. Which of these is not a pyrimidine base in DNA?
    a) Cytosine
    b) Thymine
    c) Adenine
    d) None of these
    Answer: c) Adenine
  5. Which base is replaced by uracil in RNA?
    a) Thymine
    b) Cytosine
    c) Adenine
    d) Guanine
    Answer: a) Thymine
  6. Which of the following pairs is correctly matched?
    a) Adenine – Guanine
    b) Cytosine – Adenine
    c) Guanine – Cytosine
    d) Thymine – Guanine
    Answer: c) Guanine – Cytosine
  7. What is the shape of a DNA molecule?
    a) Ladder
    b) Spiral
    c) Circular
    d) Double helix
    Answer: d) Double helix
  8. The total number of chromosomes in a human somatic cell is:
    a) 23
    b) 46
    c) 22
    d) 48
    Answer: b) 46
  9. Who discovered the double helix structure of DNA?
    a) Franklin and Pauling
    b) Avery and Griffith
    c) Watson and Crick
    d) Mendel and Morgan
    Answer: c) Watson and Crick
  10. Which sugar is found in DNA?
    a) Glucose
    b) Ribose
    c) Sucrose
    d) Deoxyribose
    Answer: d) Deoxyribose
  11. Which sugar is present in RNA?
    a) Deoxyribose
    b) Ribose
    c) Glucose
    d) Lactose
    Answer: b) Ribose
  12. A single gene controls which of the following?
    a) One protein
    b) One enzyme
    c) One amino acid
    d) One DNA strand
    Answer: a) One protein
  13. What is the functional unit of heredity?
    a) Chromosome
    b) DNA
    c) Gene
    d) Nucleosome
    Answer: c) Gene
  14. A gene is a segment of which molecule?
    a) Chromatin
    b) DNA
    c) RNA
    d) Nucleus
    Answer: b) DNA
  15. Which organelle in a cell is known as the “genetic control center”?
    a) Nucleolus
    b) Ribosome
    c) Mitochondria
    d) Nucleus
    Answer: d) Nucleus
  16. Which molecule carries genetic information from DNA to the ribosomes?
    a) mRNA
    b) tRNA
    c) rRNA
    d) snRNA
    Answer: a) mRNA
  17. Which molecule helps in protein synthesis by bringing amino acids to ribosomes?
    a) mRNA
    b) tRNA
    c) DNA
    d) snRNA
    Answer: b) tRNA
  18. Which of the following is a purine base?
    a) Cytosine
    b) Thymine
    c) Adenine
    d) Uracil
    Answer: c) Adenine
  19. Which of these bases are purines in DNA?
    a) Adenine and Guanine
    b) Guanine and Cytosine
    c) Cytosine and Thymine
    d) Adenine and Thymine
    Answer: a) Adenine and Guanine
  20. What holds the two strands of DNA together?
    a) Covalent bonds
    b) Ionic bonds
    c) Hydrogen bonds
    d) Peptide bonds
    Answer: c) Hydrogen bonds

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