Lecture 05

• What is the process of transcription in eukaryotic cells?

  Transcription is the synthesis of RNA from DNA.

  
• What are the main steps involved in RNA processing?

  Capping, splicing, and polyadenylation.

  
• What is the flow of information from gene to polypeptide?

  1. Transcription of DNA to mRNA
  2. RNA processing (capping, splicing, polyadenylation)
  3. Translation of mRNA to polypeptide
• What is the role of RNA polymerase I in eukaryotes?

  Transcription of the major rRNA transcript.
• What does RNA polymerase II transcribe?

  All protein-coding genes.

  
• What is the function of RNA polymerase III?

  Transcription of tRNA and rRNA genes.
• How are RNA polymerases distinguished?

  By their sensitivity to α-amanitin.
• What is the α-amanitin sensitivity of RNA polymerase I?

  RNA polymerase I is insensitive to α-amanitin.
• What is the α-amanitin sensitivity of RNA polymerase II?

  RNA polymerase II is extremely sensitive.
• What is the α-amanitin sensitivity of RNA polymerase III?

  RNA polymerase III is moderately sensitive.
• What is the consequence of α-amanitin toxicity?

  It causes liver failure and death.
• What are the different types of RNA produced in cells?

  • Messenger RNA (mRNA): Codes for proteins
  • Ribosomal RNA (rRNA): Forms ribosome structure
  • MicroRNA (miRNA): Regulates gene expression
  • Transfer RNA (tRNA): Adapts mRNA to amino acids
  • Other noncoding RNAs: Various functions
• What is the function of the 7-methylguanosine cap in eukaryotic mRNA?

  It protects RNA from degradation and aids translation.
• What is a typical feature of eukaryotic promoters?

  The presence of a TATA box.

  
• What is the role of transcription factors in eukaryotic transcription?

  They recognise the promoter and assist RNA polymerase binding.

  
• What is the GU-AG rule in RNA splicing?

  Introns are cut at GU and AG ends.

  
• What forms during RNA splicing in eukaryotic introns?

  A branched structure is formed.

  
• What are snRNPs in RNA splicing?

  Small nuclear ribonuclear proteins involved in splicing.

  
• What is the function of the spliceosome?

  It recognises splice sites and cuts RNA.

  
• What is the role of the TATA-box binding protein (TBP)?

  It binds to the TATA box in promoters.

  
• Is eukaryotic mRNA transcribed by RNA polymerase II?

  True, it is transcribed by RNA polymerase II.

  
• What is the poly-A tail on eukaryotic mRNA?

  It is a long string of adenine nucleotides.

  
• What is the promoter sequence in eukaryotes?

  TATAAA.

  
• What does the DNA sequence CAT specify in mRNA?

  It specifies GUA in mRNA.
• What are the steps of eukaryotic RNA processing after transcription?

  1. Capping: Addition of 7-methylguanosine cap
  2. Splicing: Removal of introns and joining of exons
  3. Polyadenylation: Addition of poly-A tail