Chapter Exam

Chapter 12: Microbial Genetics — Online MCQ Test

Q: Which enzyme removes RNA primers during DNA replication in bacteria?

Answer: B. DNA polymerase I — DNA polymerase I removes RNA primers and fills the gaps with DNA nucleotides in prokaryotes. DNA ligase later seals the remaining nicks.

Q: In the lac operon, lactose acts as a(n)

Answer: B. inducer — Lactose, specifically allolactose, induces the lac operon by inactivating the repressor. This allows transcription of the structural genes.

Q: A mutation that changes a codon into a stop codon is called a

Answer: B. nonsense mutation — A nonsense mutation converts a codon for an amino acid into a termination codon. This usually results in a shortened protein.

MICROBIOLOGY · CLASS 12th · Tamil Nadu State Board

Practice Chapter 12: Microbial Genetics with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 12th MICROBIOLOGY. This chapter covers: The final chapter explores the molecular genetics of prokaryotes and viruses. It covers DNA replication gene expression gene regulation models mutations and mechanisms of horizonta.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 12: Microbial Genetics — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 12th MICROBIOLOGY — Chapter 12: Microbial Genetics, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the semi-conservative mode of DNA replication in prokaryotes?

A. Each new DNA molecule has one old strand and one new strand ✓
B. Both strands of the old DNA remain together in one daughter molecule
C. DNA is copied without using any template strand
D. Only one strand is duplicated and the other is destroyed

Answer: A. Each new DNA molecule has one old strand and one new strand
In semi-conservative replication, each daughter DNA molecule contains one parental strand and one newly synthesized strand. This is the basic mode of DNA replication in bacteria.

Which enzyme removes RNA primers during DNA replication in bacteria?

A. DNA ligase
B. DNA polymerase I ✓
C. Helicase
D. RNA polymerase

Answer: B. DNA polymerase I
DNA polymerase I removes RNA primers and fills the gaps with DNA nucleotides in prokaryotes. DNA ligase later seals the remaining nicks.

In the lac operon, lactose acts as a(n)

A. corepressor
B. inducer ✓
C. operator
D. repressor protein

Answer: B. inducer
Lactose, specifically allolactose, induces the lac operon by inactivating the repressor. This allows transcription of the structural genes.

A mutation that changes a codon into a stop codon is called a

A. silent mutation
B. nonsense mutation ✓
C. missense mutation
D. frameshift mutation

Answer: B. nonsense mutation
A nonsense mutation converts a codon for an amino acid into a termination codon. This usually results in a shortened protein.

Which one of the following is the correct order of events in bacterial conjugation involving an F+ cell and an F− cell?

A. Plasmid integration → DNA replication → cell division
B. Pilus formation → plasmid transfer → conversion of F− to F+ ✓
C. DNA uptake → recombination → lysis
D. Phage infection → prophage formation → induction

Answer: B. Pilus formation → plasmid transfer → conversion of F− to F+
In conjugation, the F+ cell forms a sex pilus, transfers the F plasmid to the F− cell, and the recipient may become F+. This is the classic plasmid-mediated conjugation process.

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