Control of Gene Expression

• What is an operon in prokaryotes?

  A cluster of genes regulated together
• What is the function of proteins in biological processes like tryptophan synthesis?

  They are required for the synthesis process
• What are the two types of operons in prokaryotes?

  • Inducible: normally inactive, can be expressed (e.g., lac)
  • Repressible: normally expressed, can be repressed (e.g., trp)
• What type of system is the trp operon?

  A repressible system
• What type of system is the lac operon?

  An inducible system
• What role do activators play in gene expression?

  They facilitate RNA polymerase binding

  
• How are genes turned on and off in eukaryotes?

  Through complex interactions of transcription regulators

  
• What is the role of eukaryotic transcription regulators?

  • Form complexes to activate genes
  • Different combinations activate different genes
  • Some proteins can act in both activation and repression
  • Some regulators do not bind directly to DNA

  
• How do activators affect polymerase movement?

  They may regulate polymerase movement
• What happens to chromatin structure during transcriptional activation?

  • Chromatin structure is altered
  • Alterations can persist for varying lengths of time
• What is transcriptional repression in eukaryotes?

  It is the process of inhibiting gene expression
• What is the function of insulators in gene regulation?

  They ensure correct regulation of genes

  
• What is differential gene expression not caused by?

  Gene loss
• Do adult mammal cells contain all of the genome?

  Yes
• What is the significance of Dolly the sheep in gene expression studies?

  It demonstrated that adult cells retain the genome
• What is an example of a tissue-specific gene?

  PSA
• How can different cells respond to the same stimulus?

  Through differential gene expression
• What is the first step when gene expression is regulated?

  Binding site specificity
• What forms between DNA and proteins to create strong interactions?

  Hydrogen bonds
• What type of proteins are helix-loop-helix proteins?

  DNA binding proteins
• How do regulatory proteins typically bind?

  As dimers
• Why is a seven nucleotide sequence ineffective as a cis-regulatory sequence?

  It occurs too frequently in the genome
• How do transcriptional regulators bind to DNA around a nucleosome?

  More weakly than to naked DNA
• What can one transcription regulator do to a nucleosome?

  Destabilize it for another regulator's binding
• What technique is used to analyze changes in protein expression?

  2D-PAGE gels
• What is the purpose of TALENS in gene expression studies?

  To target specific genes for knockout
• How should results be compared when knocking out Htt expression?

  Against cells with Htt expression