Genetics Exam4 part2

  1. in bacteria; catabolic vs anabolic enzymes
    Catabolic enzymes degrade specific substrates; they are induced by substrates when present       A positive control

    Anabolic enzymes synthesize products; they are repressed by end-products     A negative control
  2. regulation in bacteria; operon:
    • Operon: a set of genes that is transcribed into a single mRNA from a single promoter (polycistronic)
    • Within promoter is operator
  3. regulation in bacteria; gene regulatory proteins:
    • –Gene regulatory proteins:
    • Binds to operator (regulatory site)
    • May be activators (bind and help position RNA polymerase) or repressors (block promoters)
    • Are allosteric and bind to effectors (small organic molecules such as the substrate or end-product)
    • Are constitutively expressed
  4. Regulation of the Trp Operon by the trpR Repressor
    free floating repressor is activated when tryptophan is present and can then bind to operator to repress operon by blocking RNA pol from transcribing [no more trp made]
  5. Lac Operon:
    • when lactose is absent, the repressor is bound to the lac operon and RNA pol cannot transcribe. 
    • when lactose is present it binds to repressor and changes its shape (allosteric) so it can no longer bind to operon and transcription occurs
    • lacZ: β-galactosidase (hydrolyzes lactose)
    • lacY: Galactoside permease (transports lactose into the cell)
  6. Lac Operon is positively regulated by
    • CAP/CRP activator
    • Glucose preferred energy source
    • high glucose --> low cAMP
    • low glucose  --> high cAMP
    • cAMP binds to CAP and activates it which increases RNA pol binding
  7. regulation of gene expression; levels
    • initiation of transcription
    • (pre)mRNA modification
    • mRNA stability
    • synthesis of proteins
    • modification and stability of protein
    • Image Upload 1
  8. transcription, what binds to operator?
    activator or repressor
  9. The gene that encodes for the lactose repressor
  10. some genes that tend to be expressed in all cell types
    constitutively active; housekeeping genes

    products needed all the time [synthesis of ribosomes, metabolic processes]
  11. gene expression at the genome level examples (exceptions)
    • amplification of selective genes in frog's oocytes; cells divide very fast
    • DNA arrangement producing antibodies; V,D,J segments for lymphocytes
    • Euk. DNA modification -- combined w/ histone and nonhistone proteins to form chromatin
  12. nucleosomal chromatin alteration involves histone modification and is catalyzed by...
    HATs - histone acetyltransferase enzymes -- increases transcription by loosening chromatin packing
  13. Chromatin remodeling complexes such as SWI/SNF...
    alter association of nucleosomes with DNA -- make looser or tighter
  14. DNA methylation
    • associated with less transcription; prevents binding of transcription factors
    • also Barr bodies
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Genetics Exam4 part2
Genetics Exam4 part2