Central Dogma Video <ul><li>http://www.wiley.com/legacy/college/boyer/0470003790/animations/central_dogma/central_dogma.ht...
Prokaryotic versus Eukaryotic protein synthesis Fig. 17.2ab
Four Major Steps <ul><li>Initiation </li></ul><ul><li>Elongation </li></ul><ul><li>Termination </li></ul><ul><li>Posttrans...
Parts of a Gene <ul><li>promoter  - DNA sequences which indicate the location of a gene </li></ul><ul><li>promoters are lo...
Orientation About a Gene <ul><li>RNA polymerase  – transcription enzyme (synthesizes mRNA in 5’    3’ direction) </li></u...
Initiation <ul><li>promoter regions are often sequences of A’s and T’s </li></ul><ul><ul><li>2 H-bonds between A&T </li></...
Fig. 17.6a
Initiation <ul><li>transcription factors  - numerous protein factors are involved in starting transcription </li></ul><ul>...
Elongation <ul><li>RNA polymerase synthesizes mRNA in the 5’    3’ direction </li></ul><ul><ul><li>no primer is necessary...
Elongation Nomenclature <ul><li>the template strand is the antisense strand </li></ul>5’ A T T  A C G A T C T G  C A C A  ...
 
Termination <ul><li>RNA polymerase stops transcribing once it reaches the  termination sequence </li></ul><ul><ul><li>Sign...
Termination <ul><li>termination sequences differ between prokaryotes and eukaryotes </li></ul><ul><li>Prokaryote: transcri...
Transcription
Transcription Animation <ul><li>http://www.youtube.com/watch?v=Jqx4Y0OjWW4 </li></ul>
 
Posttranscriptional Modification <ul><li>mRNA of eukaryotic cells need to be modified before moving into the cytoplasm </l...
<ul><li>5’ cap </li></ul><ul><ul><li>Modified guanine (7-methylguanosine triphosphate) added to 5’ end </li></ul></ul><ul>...
5’ 3’ 5’ cap added by  capping enzyme complex primary transcript 3’ poly-A tail added by  poly-A polymerase AAAAAAA mG mG
 
Modifications: Introns / Exons <ul><li>eukaryotic genes are longer than prokaryotic genes </li></ul><ul><ul><li>we carry e...
AAAAAAA mG exon exon exon intron intron intron intron introns removed by  spliceosome proteins AAAAAAA mG exon exon exon m...
 
Splicing Video <ul><li>http://highered.mcgraw-hill.com/olc/dl/120077/bio30.swf </li></ul>
Spliceosome Complex <ul><li>Spliceosomes are a series of  small nuclear ribonucleoproteins  (snRNP) that work together to ...
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06 transcription-stacy

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06 transcription-stacy

  1. 2. Central Dogma Video <ul><li>http://www.wiley.com/legacy/college/boyer/0470003790/animations/central_dogma/central_dogma.htm </li></ul>
  2. 3. Prokaryotic versus Eukaryotic protein synthesis Fig. 17.2ab
  3. 4. Four Major Steps <ul><li>Initiation </li></ul><ul><li>Elongation </li></ul><ul><li>Termination </li></ul><ul><li>Posttranscriptional Modification </li></ul>
  4. 5. Parts of a Gene <ul><li>promoter - DNA sequences which indicate the location of a gene </li></ul><ul><li>promoters are located upstream from the DNA region that contains the information to be transcribed into mRNA </li></ul>promoter transcription region termination sequence gene
  5. 6. Orientation About a Gene <ul><li>RNA polymerase – transcription enzyme (synthesizes mRNA in 5’  3’ direction) </li></ul><ul><li>uses upstream, promoter region to determine where to start mRNA transcription </li></ul>0 positive numbers negative numbers upstream downstream start transcription
  6. 7. Initiation <ul><li>promoter regions are often sequences of A’s and T’s </li></ul><ul><ul><li>2 H-bonds between A&T </li></ul></ul><ul><ul><li>easier to break than 3 H-bonds between G&C </li></ul></ul><ul><ul><li>prokaryotic genes have a TATA box </li></ul></ul><ul><li>dsDNA (double stranded DNA) needs to be opened for mRNA to be made </li></ul><ul><li>RNA polymerase opens the dsDNA </li></ul>
  7. 8. Fig. 17.6a
  8. 9. Initiation <ul><li>transcription factors - numerous protein factors are involved in starting transcription </li></ul><ul><li>some of these proteins help control how often genes are transcribed </li></ul>
  9. 10. Elongation <ul><li>RNA polymerase synthesizes mRNA in the 5’  3’ direction </li></ul><ul><ul><li>no primer is necessary </li></ul></ul><ul><li>template strand - only one strand of the DNA is transcribed </li></ul>
  10. 11. Elongation Nomenclature <ul><li>the template strand is the antisense strand </li></ul>5’ A T T A C G A T C T G C A C A A G A T C C T 3’ 5’ A U U A C G A U C U G C A C A A G A U C C U 3’ 3’ T A A T G C T A G A C G T G T T C T A G G A 5’ SENSE STRAND ANTISENSE STRAND DNA DNA mRNA
  11. 13. Termination <ul><li>RNA polymerase stops transcribing once it reaches the termination sequence </li></ul><ul><ul><li>Signal is actually the RNA sequence (transcribed terminator) </li></ul></ul><ul><ul><li>Eukaryote: AAUAAA </li></ul></ul><ul><li>enzyme dissociates with DNA strand and binds to another promoter sequence </li></ul>Fig. 17.6a
  12. 14. Termination <ul><li>termination sequences differ between prokaryotes and eukaryotes </li></ul><ul><li>Prokaryote: transcription ends immediately at signal </li></ul><ul><li>Eukaryote: RNAP continues for hundreds of nucleotides past termination signal; at 10-35 nucleotide past signal pre-mRNA released </li></ul>Fig. 17.8
  13. 15. Transcription
  14. 16. Transcription Animation <ul><li>http://www.youtube.com/watch?v=Jqx4Y0OjWW4 </li></ul>
  15. 18. Posttranscriptional Modification <ul><li>mRNA of eukaryotic cells need to be modified before moving into the cytoplasm </li></ul><ul><li>primary transcript – initial eukaryotic mRNA transcript, before modification </li></ul><ul><li>5’ cap – 7-methylguanosine triphosphate </li></ul><ul><li>poly-A tail – approx. 200 adenine ribonucleotides are added at the end </li></ul><ul><li>modifications prevent cellular enzymes from breaking down mRNA before it is translated into protein </li></ul>
  16. 19. <ul><li>5’ cap </li></ul><ul><ul><li>Modified guanine (7-methylguanosine triphosphate) added to 5’ end </li></ul></ul><ul><ul><li>Protect mRNA from degradation </li></ul></ul><ul><ul><li>Signals ribosome attachment </li></ul></ul><ul><li>PolyA tail </li></ul><ul><ul><li>50-250 adenine added to 3’ end </li></ul></ul><ul><ul><li>Same as 5’cap: inhibit degradation, help ribosome attach </li></ul></ul><ul><ul><li>Facilitate export of mRNA from nucleus </li></ul></ul>
  17. 20. 5’ 3’ 5’ cap added by capping enzyme complex primary transcript 3’ poly-A tail added by poly-A polymerase AAAAAAA mG mG
  18. 22. Modifications: Introns / Exons <ul><li>eukaryotic genes are longer than prokaryotic genes </li></ul><ul><ul><li>we carry extra “junk” DNA </li></ul></ul><ul><ul><li>most of this “junk” DNA signals when and how often genes should be transcribed  regulatory DNA </li></ul></ul><ul><li>primary transcript is longer than necessary </li></ul><ul><ul><li>exons – RNA sequences that will be ex pressed ; helps makes the protein </li></ul></ul><ul><ul><li>introns – in terfering RNA sequences; need to be removed before translation </li></ul></ul>
  19. 23. AAAAAAA mG exon exon exon intron intron intron intron introns removed by spliceosome proteins AAAAAAA mG exon exon exon mRNA transcript
  20. 25. Splicing Video <ul><li>http://highered.mcgraw-hill.com/olc/dl/120077/bio30.swf </li></ul>
  21. 26. Spliceosome Complex <ul><li>Spliceosomes are a series of small nuclear ribonucleoproteins (snRNP) that work together to remove introns. </li></ul><ul><li>snRNPs recognize specific sequences on the introns </li></ul><ul><ul><li>cuts out intron sequences </li></ul></ul><ul><ul><li>splices exon sequences together </li></ul></ul>

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