BIOB11H3 Lecture Notes - Lecture 5: Globin, 28S Ribosomal Rna, Ovalbumin

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17 Mar 2012
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Lecture 5 hnRNA Synthesis and Processing
SPs: Fig 11-17,18, 20, 21, 23, 24, 29
For Rrna (pol I): Initial 45s 28s, 18s, 5.8s
What about the mRNAs? Processing events?
Pulse chase strategy used (figure 11-17) mRNAs are
syntheseized as precursors
hnRNA = heterogeneous nuclear RNA
30,000 active genes many transcripts of various
sizes
- Most of newly synthesized RNA in cell is hnRNA BUT
most stable RNA of cell is Rrna (>90%)
½ life of hnrna/Mrna: MINUTES TO HOURS (AVG 40
MINS)
½ OF rRNAs: days/months; accumulation occurs
- Transcription of “pol II” gene is regulated by:
1. Transcription factors which recruits RNA pol
2. Sequences in promoter of gene binding sites for
transcription factors and binding sites for pol II. subunits
Slide 3 Lecture 5
FIGURE 11-20 There is a pre-initiation complex, yellow balls
represents the repeats that forms the tail of RNA-polymerase
When some phosphate groups are attached then they start to repel form the things binding them
They then read template and synthesize them
FIGURE11-21: mRNA features, there is a 5’ cap,5’ untranslated region, coding reasons (triplet sets that protein
encodes). 3’ uncoded region, poly alpha tail
In 5’ cap, a GTP MOLECULEGUANOSINE TRIPHOSPHATE is added to first chain to create 5’ to 5’ linkage
- Most eukaryotic genes contain both introns and exons
Cap is like a location finder to find
Untranslated parts at 3’and 5’1 are controlled in mRNA stability or ability to be translated
Tail is used in mRNA stability
Exons: Retained, instructions for protein (EXPRESSED); may also be represented as 5’ and/or 3’ untranslated
region
Introns: Interrupt exons; spliced out. HOW?
Figure11-23:
A long gene, has exons and intron
Transcription occurs with RNA polymerase, copies and makes
Adds 5’1 cap, poly-a tail added
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