Part 1: Search for Genetic Material & DNA as Genetic Material (25 MCQs)
Chapter 5 “Molecular Basis of Inheritance” is vast and one of the most important for Class 12 Biology Board and NEET UG.
Here’s the Subtopic Breakdown:
- Search for Genetic Material & DNA as Genetic Material
- Structure of DNA and RNA
- DNA Packaging in Prokaryotes and Eukaryotes
- DNA Replication & Enzymes
- Central Dogma, Transcription
- Genetic Code & Translation
- Gene Expression & Regulation – Lac Operon
- Genome Projects (Human, Rice) & DNA Fingerprinting
Part 1: Search for Genetic Material & DNA as Genetic Material (25 MCQs)
Q1. Who first discovered nucleic acids?
a) Mendel
b) Miescher
c) Watson
d) Hershey
Answer: b
- b) Correct: Friedrich Miescher discovered nuclein (DNA) in 1869.
- a) Mendel → laws of inheritance.
- c) Watson → DNA double helix.
- d) Hershey → DNA is genetic material (Hershey-Chase experiment).
Q2. Which experiment proved that DNA is the genetic material?
a) Griffith’s experiment
b) Avery, MacLeod and McCarty experiment
c) Hershey–Chase experiment
d) Meselson–Stahl experiment
Answer: c
- c) Correct: Hershey–Chase (bacteriophage experiment) proved DNA is genetic material.
- a) Griffith showed transformation principle.
- b) Avery identified transforming principle as DNA.
- d) Meselson–Stahl → semi-conservative replication.
Q3. Griffith’s experiment was conducted on:
a) Bacteriophage
b) Mice with Streptococcus pneumoniae
c) Drosophila
d) Pea plants
Answer: b
- b) Correct: Griffith used Streptococcus pneumoniae and mice → discovered transformation.
- a, c, d) Not correct.
Q4. In Griffith’s experiment, which strain of bacteria was virulent?
a) R strain
b) S strain
c) Both R and S
d) None
Answer: b
- b) Correct: S strain (smooth) was virulent, R strain was non-virulent.
Q5. Griffith concluded from his experiment that:
a) Proteins are genetic material
b) DNA is genetic material
c) Some transforming principle exists
d) RNA is genetic material
Answer: c
- c) Correct: Griffith only discovered a transforming principle, not DNA directly.
Q6. Avery, MacLeod, and McCarty showed that transforming principle was:
a) Protein
b) RNA
c) DNA
d) Lipid
Answer: c
- c) Correct: They used enzymes to degrade biomolecules, showing DNA was responsible.
Q7. Hershey and Chase used radioactive isotopes of:
a) C and N
b) S and P
c) H and O
d) Na and Cl
Answer: b
- b) Correct: ³⁵S labeled proteins, ³²P labeled DNA.
Q8. Hershey–Chase experiment used:
a) E. coli and bacteriophage T2
b) Mice and S. pneumoniae
c) Drosophila
d) Yeast
Answer: a
- a) Correct: They used bacteriophage T2 to infect E. coli.
Q9. Which statement is correct about RNA as genetic material?
a) Found in all organisms
b) Found in some viruses
c) Not stable
d) Both b and c
Answer: d
- d) Correct: RNA is genetic material in some viruses, but unstable due to reactive 2’-OH group.
Q10. RNA is genetic material in:
a) Tobacco Mosaic Virus
b) T2 phage
c) E. coli
d) Humans
Answer: a
- a) Correct: TMV has RNA as genetic material.
- b, c, d) DNA as genetic material.
Q11. Who showed that RNA can also be genetic material using TMV?
a) Watson
b) Hershey
c) Fraenkel-Conrat
d) Griffith
Answer: c
- c) Correct: Fraenkel-Conrat & Singer proved RNA as genetic material using TMV.
Q12. Which property of DNA makes it better genetic material than RNA?
a) Stability due to double helix
b) Presence of thymine instead of uracil
c) Repair mechanisms
d) All of the above
Answer: d
- d) Correct: All features make DNA better suited.
Q13. The main difference between DNA and RNA as genetic material is:
a) DNA is single-stranded, RNA is double-stranded
b) DNA is more stable, RNA is unstable
c) Both contain uracil
d) Both are unstable
Answer: b
- b) Correct: DNA = stable (due to thymine, double helix); RNA = unstable.
Q14. The transforming principle was shown to be DNA in which year?
a) 1928
b) 1944
c) 1952
d) 1953
Answer: b
- b) Correct: Avery–MacLeod–McCarty, 1944.
Q15. In Hershey–Chase experiment, after infection:
a) Radioactive sulfur entered bacteria
b) Radioactive phosphorus entered bacteria
c) Both S and P entered
d) Neither entered
Answer: b
- b) Correct: DNA (³²P) entered bacteria, proteins (³⁵S) did not.
Q16. RNA viruses use which enzyme for replication?
a) DNA polymerase
b) RNA-dependent RNA polymerase
c) Reverse transcriptase
d) DNA ligase
Answer: b
- b) Correct: RNA viruses replicate with RNA-dependent RNA polymerase.
Q17. Retroviruses replicate using:
a) DNA polymerase
b) RNA polymerase
c) Reverse transcriptase
d) Ligase
Answer: c
- c) Correct: Retroviruses → RNA to DNA using reverse transcriptase.
Q18. In Griffith’s experiment, mice died when injected with:
a) Live R strain
b) Heat-killed S strain
c) Live R + heat-killed S strain
d) Live S strain only
Answer: c
- c) Correct: Combination → live R transformed by heat-killed S.
Q19. DNA was established as genetic material in eukaryotes by studying:
a) TMV
b) Drosophila
c) Bacteriophage
d) Pneumococcus
Answer: b
- b) Correct: Eukaryotic genetics established using Drosophila.
Q20. Which is the hereditary material in most organisms?
a) Protein
b) DNA
c) RNA
d) Lipids
Answer: b
- b) Correct: DNA = universal genetic material except some viruses.
Q21. Proteins were once considered candidates for genetic material because:
a) They are stable
b) They are complex and diverse
c) They contain genetic code
d) They replicate themselves
Answer: b
- b) Correct: Proteins appeared as likely genetic material due to complexity.
Q22. Who gave the term “transformation”?
a) Avery
b) Griffith
c) Morgan
d) Hershey
Answer: b
- b) Correct: Griffith called it “transformation”.
Q23. The chemical nature of transforming principle was proved by:
a) Griffith
b) Avery, MacLeod, McCarty
c) Hershey–Chase
d) Watson and Crick
Answer: b
- b) Correct: Avery, MacLeod, McCarty identified DNA as transforming principle.
Q24. Hershey–Chase experiment finally proved that genetic material is:
a) Protein
b) DNA
c) RNA
d) Lipid
Answer: b
- b) Correct: DNA enters cell and directs viral multiplication.
Q25. DNA is preferred over RNA because:
a) It is double-stranded
b) It uses thymine, more stable
c) It has repair mechanisms
d) All of the above
Answer: d
- d) Correct: All reasons make DNA superior.
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