Genetics Chapter 12

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Genetics Chapter 12
2012-07-22 19:59:37
Genetics Chapter 12 Dr Troy Bray

Genetics Chapter 12 Dr. Troy Bray
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  1. what is the central dogma of genetics?
    DNA can replicate, goes through transcription to make RNA and RNA goes through translation to make protien
  2. gene
    • segment of DNA that is sued to make a functional product
    • RNA or polypeptide
  3. structural gene
    • encodes the amino acid sequences of a polypeptide 
    • 90% of all genes
  4. promoter
    • sequences tht specifies a site to being transcription 
    • cause RNA synthesis to occur within a defined location
  5. terminator
    • sequence tht specifies a site to end transcription
    • cause RNA synthesis to occur within a defined location
  6. RNA transcript is complementary to the _____ strand
    • template 
    • aka antisense
    • aka noncoding
  7. in structural genes, the non-template DNA is called _____ or ____ 
    • coding 
    • sense
  8. what are transcription factors
    proteins that recognize base sequences in DNA and control transcription
  9. some transcription factors bond to _____ and initiate transcription
  10. some transcription factors bind to _____ ______ and either increase or decrease the rate of transcription
    regulatory sequences
  11. three steps in transcription
    • initiation 
    • elongation/ sythesis
    • termination
  12. transcription in bacteria
    • promoter directs the exact loation for the initiation of RNA transcription 
    • located just upstream from the site where transcription of a structural gene begins 
  13. upstream
    negative positions
  14. downstream
    positive positions
  15. transcription start site
  16. sequence elements
    • short sequences within promoter regions that are cirtically important for the recognition of promoters 
    • two important sequences are located at ~-35 and -10 positions
  17. typical bacterial promoter
    • pribnow box
    • sequences at the regions can vary from gene to gene 
  18. pribnow box
    • sequence at -10 region 
    • 5'-TATAAT-3'
  19. consensus precentage
    • sequences at these regions can vary gene to gene
    • line up sequences and highlig like bases and calculate percentages
  20. core enzyme
    • holoenzyme 
    • 5 subunits + sigma factor
  21. function of alpha subunit of core enzyme
    binding polymerase to DNA
  22. function of beta and beta prime subunit
    synthesizing or catalyzing the synthesis of RNA
  23. function of omega subunit 
    responsible for the core enzyme assembly 
  24. sigma factor
    • recognizes the promoter sequence
    • contains helix-turn-helix motif that binds tightly to the DNA
    • occurs in the major groove of DNA double helix
    • hydrogen bonding between -35 and -10 nucleotide of the promoter and AA side chain in the helix-turn-helix structure of the sigma factor
  25. elongation stage 
    • RNA polymerase along the DNA causing it to unwind (form open complex of ~17bp)
    • RNa polymerase synthesis averages 43 nucleotides/second in the 5' to 3' direction
    • begind the open complex, the DNA rewinds back into a double helix
  26. transcription termination
    • when shor RNA-DNA hybrid region is forced to sepatate
    • releases newly made RNA transcript and RNA polymerase form template
  27. two different termination mechanisms in E. coli
    • rho dependent 
    • rho independent
  28. rho dependent termination
    • sequences near the 3' end of the newly made mRNA called the rut site is recognized and bound by the rho protein (helicase)
    • depends on rho proteins
    • rut= rho utilization
  29. rho independent termination
    • loop that causes RNA polymerase to pause at a U-rich sequence which is thought t be unstable causing RNA polymerase to spontaneously dissociate from DNA
    • uracil rich region causes the polymerase to disassociate 
    • no protein required for physical removal