Gene Expression Practice Questions
19 free Gene Expression practice questions for the Microbiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is the first step of gene expression in microbes?
- A Translation
- B Replication
- C Transcription
- D Transformation
Correct answer: Transcription
Gene expression begins with transcription, where DNA is converted into RNA. This step is essential for transferring genetic information from DNA to RNA.
Which enzyme is responsible for transcription in bacteria?
- A RNA polymerase
- B DNA polymerase
- C Ligase
- D Helicase
Correct answer: RNA polymerase
RNA polymerase synthesizes RNA from a DNA template during transcription. It binds to promoter regions to initiate the process.
Which RNA molecule carries genetic information from DNA to ribosomes?
- A tRNA
- B rRNA
- C snRNA
- D mRNA
Correct answer: mRNA
Messenger RNA (mRNA) carries the genetic code from DNA to the ribosome. It serves as the template for protein synthesis.
What is the function of tRNA in gene expression?
- A Carries amino acids to ribosome
- B Synthesizes RNA
- C Binds DNA
- D Forms the structural core of ribosomes
Correct answer: Carries amino acids to ribosome
Transfer RNA (tRNA) brings specific amino acids to the ribosome during translation. It matches its anticodon with the mRNA codon.
Which structure is the site of protein synthesis in microbes?
- A Nucleus
- B Golgi apparatus
- C Mitochondria
- D Ribosome
Correct answer: Ribosome
Ribosomes are the sites where translation occurs. They read mRNA sequences and assemble amino acids into proteins.
What is a promoter in gene expression?
- A Protein-coding region of the structural gene
- B Termination signal
- C RNA processing site
- D DNA sequence where RNA polymerase binds
Correct answer: DNA sequence where RNA polymerase binds
A promoter is a DNA sequence that signals the start of transcription. RNA polymerase binds here to begin RNA synthesis.
Which sequence signals the end of transcription?
- A Operator sequence
- B Enhancer
- C Terminator
- D Codon
Correct answer: Terminator
A terminator sequence signals RNA polymerase to stop transcription. This releases the newly synthesized RNA molecule.
Which codon signals the start of translation in most microbes?
- A UAA
- B UGA
- C AUG
- D UAG
Correct answer: AUG
AUG is the start codon and codes for methionine. It signals the beginning of protein synthesis during translation.
What is an operon?
- A Single gene under one regulatory element
- B Cluster of genes under one promoter
- C Complex of proteins binding to DNA
- D Non-coding RNA regulating translation
Correct answer: Cluster of genes under one promoter
An operon is a group of genes regulated together under a single promoter. It allows coordinated gene expression in microbes.
Which operon is involved in lactose metabolism in E. coli?
- A Trp operon
- B Lac operon
- C His operon
- D Ara operon
Correct answer: Lac operon
The lac operon controls genes required for lactose utilization. It is activated when lactose is present and glucose is low.
What is the role of a repressor protein?
- A Enhances transcription by recruiting activators
- B Binds promoter to start transcription
- C Blocks transcription by binding operator
- D Synthesizes RNA from a DNA template strand
Correct answer: Blocks transcription by binding operator
A repressor protein binds to the operator region and prevents RNA polymerase from transcribing genes. This inhibits gene expression.
Which molecule inactivates the lac repressor?
- A Glucose
- B Lactose
- C ATP
- D DNA
Correct answer: Lactose
Lactose (or its derivative allolactose) binds to the repressor and inactivates it. This allows transcription of lac operon genes.
What is the role of ribosomal RNA (rRNA)?
- A Carries amino acids to the site of protein synthesis
- B Forms ribosome structure and catalyzes peptide bonds
- C Carries the genetic code to the site of translation
- D Synthesizes DNA during the process of cell replication
Correct answer: Forms ribosome structure and catalyzes peptide bonds
rRNA is a structural and catalytic component of ribosomes. It helps form peptide bonds between amino acids during translation.
What is the direction of mRNA synthesis during transcription?
- A 3' to 5'
- B 5' to 3'
- C Both directions
- D Random
Correct answer: 5' to 3'
mRNA is synthesized in the 5' to 3' direction. RNA polymerase reads the DNA template strand in the 3' to 5' direction.
Which of the following is a key difference between prokaryotic and eukaryotic gene expression?
- A Presence of ribosomes in the cytoplasm
- B Coupled transcription and translation
- C Use of mRNA to direct protein synthesis
- D DNA replication using similar enzymes
Correct answer: Coupled transcription and translation
In prokaryotes, transcription and translation occur simultaneously in the cytoplasm. This is not seen in eukaryotes due to compartmentalization.
What is the role of sigma factor in bacteria?
- A Terminates transcription by releasing mRNA
- B Binds ribosome to start translation
- C Helps RNA polymerase recognize promoter
- D Synthesizes protein from the mRNA code
Correct answer: Helps RNA polymerase recognize promoter
Sigma factor directs RNA polymerase to specific promoter sequences. It is essential for the initiation of transcription.
Which type of RNA contains anticodons?
- A mRNA
- B rRNA
- C tRNA
- D snRNA
Correct answer: tRNA
tRNA contains anticodons that are complementary to mRNA codons. This ensures correct amino acid incorporation during translation.
What is the process of converting mRNA into protein called?
- A Replication
- B Transcription
- C Translation
- D Recombination
Correct answer: Translation
Translation is the process where ribosomes read mRNA and synthesize proteins. Amino acids are assembled into polypeptide chains.
Which molecule provides energy for translation?
- A NADH and FADH2
- B Amino acids
- C Ribosomes
- D ATP and GTP
Correct answer: ATP and GTP
ATP and GTP provide energy for various steps of translation, including tRNA charging and ribosome movement. These energy molecules ensure efficient protein synthesis.