Chapter 11 - The Control of Gene Expression

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Chapter 11 - The Control of Gene Expression

• Eukaryotic Gene Regulation

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• DNA is packed in to the nucleus
• Histones
• Nucleosomes
• Helical fiber
• Supercoil
• Chromosome
• What does this have to do with gene expression?

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• Female mammals
• One X chromosome of each cell is highly compacted
  and inactive
• Random, early in development
• Inactivity inherited as cell divides
• Heterozygous females have cells of 2 distinct
  genotypes and phenotypes (Cat example)

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• Control of transcription in eukaryotes
• More complex than prokaryotic regulation
• Most genes have own promoters and other control
  sequences
• Activators more important than repressors
• Most genes off
• So, how are most genes turned on?

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• Transcription factors
• Proteins (like activators) work with RNA
  polymerase
• Enhancers regions of DNA to which activators
  bind
• Activators bind to enhancersother factors bind
  to the promoter.
• DNA bends
• RNA polymerase has access to gene, transcription
  begins

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• Regulating gene expression during splicing
• RNAs exit from the nucleus
• Alternative RNA splicing
• A single gene can produce different mRNAs and,
  therefore, different polypeptides
• Insert alernative splicing picture

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• Regulation during translation and after
• regulating life span of mRNA
• regulating proteins involved in translation
• Polypeptide alteration
• Insulin example
• Insert insulin picture
• Breaking down proteins

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