BIO 120 Chapter 18

  1. Negative Feedback
    Keeps things the same in cells
  2. Tryptophan and Enzyme 2 and 3
    When Tryptophan is present, it makes Enzymes 2 and 3 are almost useless because they won't be made
  3. Operator
    • segment of DNA positioned within the promoter that acts as regulatory "switch"
    • part of the operon
  4. Operon
    • entire stretch of DNA that includes the operator, promoter, and genes they control
    • can be switched off when protein repressor is present (repress means off)
  5. Two Types of Negative Gene Regulation
    • Repressible operons
    • Inducible operons
  6. Repressible operon
    • binding of repressor to operator shuts off transcription
    • usually on, making the repressor usually inactive
  7. Inducible operon
    • inducer inactivates repressor and turns on transcription
    • usually off, making the repressor usually active
  8. trp operon
    When the repressor is inactive, transcription occurs
  9. Presence of lactose
    Transcription occurs
  10. Lac Operon
    • inducible
    • normally off because the repressor is normally active
  11. Beta-Galactosidase
    only produced when there is lactose
  12. Gene expresssion in eukaryotic cells
    Can be regulated at any stage
  13. Chromatin
    long, stringy form of DNA
  14. Histone acetylation and DNA methylation
    regulate transcription by regulating the chromatin
  15. Histone acetylation
    • acetyl groups are attached to lysines in histone tails
    • loosens chromatin structure; promotes initiation of transcription
  16. DNA methylation
    • addition of methyl groups to certain bases in DNA
    • reduces transcription
  17. Post-transcriptional regulation
    • has to do with mRNA splicing
    • 1) mRNA degradation
    • 2) initiation of translation
    • 3) protein processing and degradation
  18. RNA interference (RNAi)
    inhibition of gene expression by RNA molecules
  19. Gene expression during embryonic debelopment
    The transformation from zygote to adult results from cell division, cell differentiation, and morphogenesis.
  20. Cytoplasmic determinants
    • maternal substances in the egg that influence early development
    • first place where differentiation occurs
  21. Pattern formation
    • development of a spatial organization of tissues and organs
    • begins with establishment of the major axes (animals)
  22. Positional formation
    tells a cell its location relative to the body axes and to neighboring cells
Card Set
BIO 120 Chapter 18
Regulation of gene expression