Regulation of Gene Activity

1
Regulation of Gene Activity
2
Conservation

• Remember, our bodies are conservative, they only
  make what we need, when we need it.
• How do they know this???

3
Operon

• Jacob and Monod E. coli capable of regulating
  the expression of its genes
• Regulator gene codes for repressor
• Repressor controls whether the operon is active
  or not.

4
Operon

• Promoter - DNA, beginning of gene to be
  transcribed, signals the start of a gene
• Operator portion of DNA where repressor binds,
  controls mRNA synthesis
• When repressor binds here, RNA polymerase cannot
  attach to the promoter, prevents transcription
• Structural genes codes for primary structure of
  enzyme to be transcribed.

5
trp operon

• Exist in on position repressible
• Products 5 different enzymes, synthesis of AA
  tryptophan
• If tryptophan is already present, it binds to
  repressor, which then binds to operator and no
  transcription takes place.

6
lac operon

• Makes 3 enzymes needed for metabolism of lactose
• When lactose is present, it binds to the
  repressor, and repressor cannot bind to operator,
  therefore transcription takes place
• Lactose is an inducer, inducible operon

7
Eukaryotic regulation

• 5 primary levels of control
• Chromatin structure
• Transcriptional control transcriptional factors
  initiate/regulate transcription
• Posttranscriptional control mRNA processing and
  how fast mRNA leaves the nucleus
• Translational control when translation begins
  and how long it continues
• Posttranslational control after protein
  synthesis, polypeptide may have to undergo
  additional changes before it is functional.

8
Chromatin structure

• Levels of chromatin organization is related to
  the degree that the nucleosomes coil.
• Heterochromatin highly condensed chromatin,
  inactive
• Barr Body- only in females, small, dark,
  condensed chromatin, inactive X chromosome
• Euchromatin loosely compacted chromatin,
  potentially active, genes expressed.

9
Genetic mutations

• Point mutations change in a single DNA
  nucleotide, change in specific codon
• Frameshift muations one or more nucleotides are
  inserted or deleted
• Nonfunctional proteins can have dramatic
  effects on phenotype

10
carcinogenesis

• When proto-oncogenes mutate, they become
  oncogenes.
• Tumor suppressor genes usually act to stop cell
  division if there is a problem.
• Cancer loss of TSG and activity of oncogene
  uncontrollable cell division