Transcription Page 319 324 Example problems Page 324
Transcription Page 319 -324 Example problems: Page 324, #2, 3, 9
Transcription �The process of making… �RNA review �Very similar to DNA except: � Has a ribose sugar instead of a deoxyribose � Uses � Is the base uracil instead of thymine generally single-stranded
Video �Transcription Video
Types of RNA �m. RNA: messenger RNA �t. RNA: transfer RNA �r. RNA: ribosomal RNA
Steps of Transcription 1. Initiation 2. Elongation 3. Termination
RNA Polymerase �The enzyme responsible for making RNA �In prokaryotes: �Only 1 RNA polymerase �In eukaryotes: �RNA Polymerase II: responsible for… �RNA Polymerase I and III: responsible for…
Transcription Initiation �What happens? �Promoter: � Generally high in A’s and T’s…WHY? � TATA box � TATAAT
Transcription Initiation �Promoter: gene promoter transcription region termination sequence
Transcription Initiation upstream negative numbers downstream +1 start transcription positive numbers
Transcription Elongation � 5’ 3’ �Template strand
2. Transcription Elongation DNA 5’ A T T A C G A T C T G C A A G A T C C T 3’ 3’ T A A T G C T A G A C G T T C T A G G A 5’ m. RNA 5’ A U U A C G A U C U G C A A G A U C C U 3’ Antisense strand: Sense strand: SENSE STRAND ANTISENSE STRAND
Transcription Bubble
3. Transcription Termination sequences differ between prokaryotes and eukaryotes
Post-transcriptional modifications �Primary transcript �Modifications are done to stabilize and protect the RNA �Poly(A) tail: � Enzyme? � 5’ cap: � Enzyme? � Unusual 5’-to-5’ triphosphate linkage
4. Posttranscriptional Modification primary transcript 5’ 3’ 5’ cap added by capping enzyme complex m. G 3’ poly-A tail added by poly-A polymerase m. G AAAAAAA
Post-transcriptional modifications �Splicing; �exons – expressed �introns – interfering
4. Posttranscriptional Modification m. G intron exon intron AAAAAAA introns removed by spliceosome proteins m. G exon AAAAAAA m. RNA transcript
4. Posttranscriptional Modification Spliceosomes are a series of small nuclear ribonucleoproteins (sn. RNP) sn. RNPs: �cuts out intron sequences �splices exon sequences together
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