6.5 Regulation of Gene Expression

Describe the types of interactions that regulate gene expression.

• Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription. Some genes are constitutively expressed, and others are inducible.
• Epigenetic changes can affect gene expression through reversible modifications of DNA or histones.
• The phenotype of a cell or an organism is determined by the combination of genes that are expressed and the levels at which they are expressed.
  • i. Observable cell differentiation results from the expression of genes for tissue-specific proteins.
  • ii. Induction of transcription factors during development results in sequential gene expression.
  • iii. The function and amount of gene products determine the phenotype of organisms.

Explain how the location of regulatory sequences relates to their function.

• Both prokaryotes and eukaryotes have groups of genes that are coordinately regulated.
  • i. Prokaryotes regulate operons in an inducible or repressible system.
  • ii. In eukaryotes, groups of genes may be influenced by the same transcription factors to coordinately regulate expression. 119 Gene Expression and Regulation UNIT 6