Genetics Ch 12: Prok Transcription

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Last updated 4:36 PM on 4/15/26
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23 Terms

1
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__________ genes = transcribed and translated

  • aka ________-coding genes

  • 90% of genes

__________ genes = transcribed, but not translated (function as RNA)

  • ex: ribosomes, spliceosomes, signal recognition particle, telomerase

structural genes = transcribed and translated

  • aka protein-coding genes

  • 90% of genes

non-structural genes = transcribed, but not translated (function as RNA)

  • ex: ribosomes, spliceosomes, signal recognition particle, telomerase

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Bacterial gene sites for transcription

  1. __________ = sites for binding regulatory transcription factor proteins

    • increases or decreases rate of transcription

  2. __________ = site for RNA pol binding = beginning of transcription

  3. __________ = site that signals end of transcription

  4. __________ = site for ribosome binding to mRNA in bacteria

    • ribosome scans RNA for start codon

    • translation beings here

    • in eukaryotes, ribosome binds to _________ cap in mRNA

Bacterial gene sites for transcription

  1. regulatory elements = sites for binding regulatory transcription factor proteins

    • increases or decreases rate of transcription

  2. promoter = site for RNA pol binding = beginning of transcription

  3. terminator = site that signals end of transcription

  4. ribosome-binding site = site for ribosome binding to mRNA in bacteria

    • ribosome scans RNA for start codon

    • translation beings here

    • in eukaryotes, ribosome binds to 7-methylguanosine cap in mRNA

<p>Bacterial gene sites for transcription</p><ol><li><p><strong>regulatory elements</strong> = sites for binding regulatory transcription factor proteins</p><ul><li><p>increases or decreases rate of transcription</p></li></ul></li><li><p><strong>promoter</strong> = site for RNA pol binding = beginning of transcription</p></li><li><p><strong>terminator</strong> = site that signals end of transcription</p></li><li><p><strong>ribosome-binding site</strong> = site for ribosome binding to mRNA in bacteria</p><ul><li><p>ribosome scans RNA for start codon</p></li><li><p>translation beings here</p></li><li><p>in eukaryotes, ribosome binds to <u>7-methylguanosine</u> cap in mRNA</p></li></ul></li></ol><p></p>
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codons are on ______ and anticodons are on ______

codons are on mRNA and anticodons are on tRNA

<p>codons are on <u>mRNA</u> and anticodons are on <u>tRNA</u></p>
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bacterial mRNA are __________ = one mRNA → many polypeptides

  • each mRNA can have many start/stop codons

polycistronic

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nontemplate/template strand = transcribed strand, complementary to to mRNA

nontemplate/template strand = not transcribed, identical to mRNA

template strand = transcribed strand, complementary to to mRNA

nontemplate strand = not transcribed, identical to mRNA

<p><strong>template strand </strong>= transcribed strand, complementary to to mRNA</p><p><strong>nontemplate strand</strong> = not transcribed, identical to mRNA</p>
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template = sense/antisense = coding/noncoding

nontemplate = sense/antisense = coding/noncoding

template = antisense = noncoding

nontemplate = sense = coding

<p>template = <strong>antisense</strong> = <strong>noncoding</strong></p><p>nontemplate = <strong>sense</strong> = <strong>coding</strong></p>
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promoters = promote gene expression

  • direct location for start of transcription

  • upstream/downstream where transcription begins

    • in other words, at __’ of nontemplate strand

  • contain numbering system relative to transcription start site

promoters = promote gene expression

  • direct location for start of transcription

  • upstream where transcription begins

    • in other words, at 5’ of nontemplate strand

  • contain numbering system relative to transcription start site

<p>promoters = promote gene expression</p><ul><li><p>direct location for start of transcription</p></li><li><p><u>upstream</u> where transcription begins</p><ul><li><p>in other words, at <u>5</u>’ of nontemplate strand</p></li></ul></li><li><p>contain <em>numbering system</em> relative to transcription start site</p></li></ul><p></p>
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__________ = common sequences

  • most common are _____ and _____ sequences

  • results in high/low transcription

    • if promoter deviates from consensus sequence → high/low transcription

consensus sequence = common sequences

  • most common are -35 and -10 sequences

  • results in high transcription

    • if promoter deviates from consensus sequence → low transcription

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__________ = catalyzes synthesis of RNA

RNA pol

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RNA pol

  • core enzyme = ________

  • holoenzyme = ________

RNA pol

  • core enzyme = ɑ2ββ’⍵

  • holoenzyme = ɑ2ββ’⍵σ

    • contains core enzyme + sigma factor

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Transcription contains 3 stages:

  1. Initiation

  2. Elongation

  3. Termination

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Initiation of Transcription (1/4)

  1. RNA pol holoenzyme binds _____ to DNA

  2. scans DNA for _______ region

Initiation of Transcription (1/4)

  1. RNA pol holoenzyme binds loosely to DNA

  2. scans DNA for promoter region

<p>Initiation of Transcription (1/4)</p><ol><li><p>RNA pol holoenzyme binds <u>loosely</u> to DNA</p></li><li><p>scans DNA for <u>promoter</u> region</p></li></ol><p></p>
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Initiation of Transcription (2/4)

  1. ________ recognizes promoter region by -10 and -35 sequences

    • contains ____________ and involved in ________ binding

  2. RNA pol binding to promoter → _____ complex

Initiation of Transcription (2/4)

  1. sigma factor (σ) recognizes promoter region by -10 and -35 sequences

    • contains helix-turn-helix and involved in tighter binding

  2. RNA pol binding to promoter → closed complex

<p>Initiation of Transcription (2/4)</p><ol start="3"><li><p><strong>sigma factor (</strong><span style="background-color: transparent;"><strong>σ)</strong></span> recognizes promoter region by -10 and -35 sequences</p><ul><li><p>contains <u>helix-turn-helix</u> and involved in <u>tighter</u> binding</p></li></ul></li><li><p>RNA pol binding to promoter → <strong>closed complex</strong></p></li></ol><p></p>
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Initiation of Transcription (3/4)

  1. TATAAAT box in ___ region is unwound → _____ complex

    • AT bonds can be easily separated

Initiation of Transcription (3/4)

  1. TATAAAT box in -10 region is unwound → open complex

    • AT bonds can be easily separated

<p>Initiation of Transcription (3/4)</p><ol start="5"><li><p>TATAAAT box in <u>-10</u> region is unwound → <strong>open complex</strong></p><ul><li><p>AT bonds can be easily separated</p></li></ul></li></ol><p></p>
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Initiation of Transcription (4/4)

  1. short RNA strand made in open complex

    • _______ is released

Initiation of Transcription (4/4)

  1. short RNA strand made in open complex

    • sigma factor is released

<p>Initiation of Transcription (4/4)</p><ol start="6"><li><p>short RNA strand made in open complex</p><ul><li><p><u>sigma factor</u> is released</p></li></ul></li></ol><p></p>
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Elongation during Transcription (1/3)

  • open complex is about ___ bases long

  • rate of RNA synthesis = ___ nucleotides/second

Elongation during Transcription (1/3)

  • open complex is about 17 bases long

  • rate of RNA synthesis = 43 nucleotides/second

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Elongation during Transcription (2/3)

  • RNA pol synthesizes RNA from __’ → __’

  • RNA pol slides along template from __’ → __’

Elongation during Transcription (2/3)

  • RNA pol synthesizes RNA from 5’ → 3’

  • RNA pol slides along template from 3’ → 5’

<p>Elongation during Transcription (2/3)</p><ul><li><p>RNA pol synthesizes RNA from <u>5</u>’ → <u>3</u>’</p></li><li><p>RNA pol slides along template from <u>3</u>’ → <u>5</u>’</p></li></ul><p></p>
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Elongation during Transcription (3/3)

  • precursors = __________

  • __________ is released

Elongation during Transcription (3/3)

  • precursors = nucleoside triphosphates

  • pyrophosphate (PPi) is released

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Both strands may / may not be used as template

Both strands may be used as template

<p>Both strands <u>may</u> be used as template</p>
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Rho-dependent termination = requires ⍴ (1/3)

  1. ______ protein binds to ____ site on RNA and moves to 3’ end

Rho-dependent termination (1/3)

  1. ⍴ (rho) protein binds to rut site on RNA and moves to 3’ end

<p>Rho-dependent termination (1/3)</p><ol><li><p><span style="background-color: transparent;"><strong>⍴ (rho)</strong></span> protein binds to <strong>rut</strong> site on RNA and moves to 3’ end</p></li></ol><p></p>
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Rho-dependent termination (2/3)

  1. RNA pol transcribes _____ loop (causing RNA pol to _____) and goes to terminator

Rho-dependent termination (2/3)

  1. RNA pol transcribes stem loop (causing RNA pol to pause) and goes to terminator

<p>Rho-dependent termination (2/3)</p><ol start="2"><li><p>RNA pol transcribes <u>stem</u> loop (causing RNA pol to <u>pause</u>) and goes to terminator</p></li></ol><p></p>
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Rho-dependent termination (3/3)

  1. During pause, rho can reach open complex to separate ________

Rho-dependent termination (3/3)

  1. During pause, rho can reach open complex to separate RNA-DNA hybrid

<p>Rho-dependent termination (3/3)</p><ol start="3"><li><p>During pause, rho can reach open complex to separate <u>RNA-DNA hybrid</u></p></li></ol><p></p>
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Rho-independent termination = does not require ⍴

RNA contains ______-rich sequence at 3’ end

  1. Like rho-dependent termination, terminator causes stem loop so RNA pol pauses

  2. ______-rich sequence is weak => RNA-DNA hybrid collapses without rho

Rho-independent termination = does not require ⍴

RNA contains uracil-rich sequence at 3’ end

  1. Like rho-dependent termination, terminator causes stem loop so RNA pol pauses

  2. uracil-rich sequence is weak => RNA-DNA hybrid collapses without rho

<p><strong>Rho-independent termination</strong> = does not require <span style="background-color: transparent;">⍴ </span></p><p>RNA contains <u>uracil</u>-rich sequence at 3’ end</p><p></p><ol><li><p>Like rho-dependent termination, terminator causes stem loop so RNA pol pauses</p></li><li><p><u>uracil</u>-rich sequence is weak =&gt; RNA-DNA hybrid collapses without rho</p></li></ol><p></p>