Gene Regulation

Prokaryotes vs. Eukaryotes

Prokaryotes

• DNA in the cytoplasm

• NAked DNA

• Circular chromosome

• No introns

Eukaryotes

• DNA in nucleus

• Linear

• DNA wond on histones to fit in nucleus

• Introns and Exons are present

Gene transcription

Constitutive genes

• Gens that are always expressed and never regulated

  • Proteins made from these gens are necessary for the survival of the cell

• Most genes are turned on or off

Bacterial Metabolism

Bacteria need to respond quickly to changes in their environment

• If they have enough of product -→ stop production

  • Waste of energy to create an overabundance of a substance

• If they find a new food/enrgy source → need to use it quick

Gene expression in Prokaryotes

• Transcription and Translation can occur at he same time in bacteria

  • DNA in the cytoplasm

  • No mRNA modifications

  • Ribosomes read mRNA as it is being transcribed

Gene Regulation

Feedback inhibition

• Instead of blocking enzyme function, block transcription genes for all enzymes in the pathway

  • Saves energy by not wasting it on unecessary protein synthesis

Bacteria group genes together

Operon -a functional unit of transcription and regulation

• transcribes all the proteins in a pathway

  • Ex. All enzymes in a metabolic pathway

• Promoter = RNA polymerase binding site

  • Single promoter controls transcription of all genes in operon

  • Transcribed as one unit - single mRNA is made

• Operon

  • Site where repressor proteins bind to

• Regulatory gene = DNA that codes for repressir/inducer