Lecture 04

• What is the typical structure of a gene?

  It includes coding and regulatory sequences.

  
• What are gene families?

  Groups of related genes with similar sequences.
• What is the process of transcription in bacterial cells?

  It synthesises RNA from a DNA template.

  
• What is the nature of a promoter?

  It is a DNA sequence where transcription starts.

  
• What is the function of RNA polymerases?

  They synthesise RNA from a DNA template.

  
• What are the three stages of transcription?

  Initiation, elongation, and termination.

  
• What is the size of the human genome?

  3.1 x 10^9 bp
• How many protein-coding genes are in the human genome?

  Less than 20,000
• What does the central dogma state?

  Genetic information flows from DNA to RNA to protein.

  
• What is the role of mRNA in protein synthesis?

  It is a copy of a gene that directs protein synthesis.
• What is a gene in its simplest form?

  A DNA segment coding for a polypeptide sequence.
• What are introns?

  Non-coding regions that interrupt exons in genes.
• What is the typical length range of introns?

  50 bp to 100 bp
• What are exons?

  Sequences that encode amino acids in proteins.
• What is the length range of exons?

  50 bp to a few kilobases
• What is the dystrophin gene associated with?

  Duchenne muscular dystrophy (DMD)
• What happens when there are mutations in the dystrophin gene?

  They can lead to muscle degeneration and weakness.
• How long is the dystrophin gene?

  2500 kb
• What is the length of the corresponding mRNA for the dystrophin gene?

  14 kb
• What percentage of the dystrophin gene consists of coding exons?

  Less than 1%
• What are pseudogenes?

  Non-functional genes that have accumulated mutations.
• What is the significance of the holoenzyme in prokaryotic transcription?

  It is crucial for initiating transcription.

  
• What is intrinsic termination in transcription?

  It signals the end of transcription without extra proteins.

  
• What is extrinsic termination in transcription?

  It requires additional proteins like the Rho factor.

  
• What are the steps involved in transcription?

  1. Binding of RNA polymerase to the promoter
  2. Initiation of RNA synthesis
  3. Elongation of the RNA strand
  4. Recognition of termination signal
  5. Cessation of transcription
  6. Release of RNA from DNA

  
• What are the differences between replication and transcription?

  Replication:

  • DNA polymerase
  • More accurate
  • Longer DNA molecules
  • Both strands copied

  
  

  Transcription:

  • RNA polymerase
  • Frequent mistakes
  • Shorter RNA transcripts
  • One strand copied
• What are the similarities between replication and transcription?

  • Polymerases have several subunits
  • Many proteins involved
  • Synthesis occurs in 5’-3’ direction
  • Both processes involve initiation and elongation