lecture 24 - eukaryotic gene regulation ii

• How does chromatin structure affect gene expression in eukaryotes?

  It influences the accessibility of genes for transcription.
• What is a “control element” in gene regulation?

  A DNA sequence that regulates gene expression.
• How do control elements and transcription factors work together?

  They combine to regulate gene expression.
• What effect does RNA processing have on gene expression?

  It modifies RNA transcripts, influencing their stability and translation.

  
• How can we determine the “steady state” levels of expression in a cell?

  By measuring the rates of synthesis and degradation of mRNA and proteins.
• What roles do non-coding RNAs play in gene expression control?

  They regulate gene expression at various levels.
• What is required for RNA polymerase to bind to a promoter in eukaryotes?

  The action of general transcription factors.
• How do specific transcription factors interact with enhancers?

  They can interact with the transcription initiation complex via DNA bending.
• What happens when the green, blue, and yellow activators are present in a cell?

  • Activators bind to their corresponding enhancer elements.
  • Genes associated with these enhancers will be transcribed.
• How do activators ensure transcription of appropriate genes in different cell types?

  • Specific activators are present in nerve cells for nerve-specific genes.
  • Different activators are present in skin cells for skin-specific genes.
• What is the significance of alternative splicing in eukaryotic genomes?

  It expands the repertoire of proteins that can be produced from a single gene.

  
• What percentage of human protein-coding genes undergo alternative splicing?

  More than 90%
• What determines the steady-state level of mRNA and protein?

  The rate of synthesis and the rate of degradation.
• What modifications are made to pre-mRNA?

  The 5’ cap and poly-A tail are added.

  
• What is the function of the 5’ cap on mRNA?

  It helps ribosomes attach to the mRNA.

  
• What does the poly-A tail do for mRNA?

  It prevents the mRNA from being hydrolyzed.

  
• What does Ube3A encode?

  An enzyme, ubiquitin ligase.

  
• What is the role of Ube3A in protein regulation?

  It tags proteins with ubiquitin for degradation.

  
• What is the significance of non-coding DNA in the human genome?

  It comprises 98% of the genome and does not code for amino acids.
• What discovery was awarded the 2024 Nobel Prize in Physiology & Medicine?

  The discovery of microRNA and its role in post-transcriptional gene regulation.
• What do microRNAs (miRNAs) do?

  They bind to mRNA and can cause degradation or block translation.

  
• What is the biogenesis process of miRNA?

  1. Transcription of microRNA gene
  2. Processing by Drosha
  3. Export out of the nucleus by Exportin5
  4. Processing by Dicer to create mature miRNA
  5. Loading into the RNA-Induced Silencing Complex (RISC)
  6. Repression of gene expression based on complementarity

  
• What is RNA interference (RNAi)?

  A process where siRNA blocks gene expression.

  
• How are small interfering RNAs (siRNAs) similar to miRNAs?

  They are similar in size and function.

  
• What are the key components of gene expression regulation in eukaryotes?

  • Transcription and processing of mRNA
  • mRNA degradation
  • Translation and processing of proteins
  • Protein degradation