Announcements. Tuesday afternoon lab section: lab start time next week is 3pm. 2-3 pm might be a good time to do problem set 6! 2. No advance reading for next week’s lab; focus on your lab report. 3. Problem set 5 due at start of class today. 4. Reading - Ch. 16: skip btm. 442- top 444.
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Tuesday afternoon lab section: lab start time
next week is 3pm. 2-3 pm might be a good time to do problem set 6!
2. No advance reading for next week’s lab; focus on your lab report.
3. Problem set 5 due at start of class today.
4. Reading - Ch. 16: skip btm. 442- top 444.
1.The lac operon - in detail; know roles of all components
2. The trp operon - very briefly
I. Eukaryotic Gene Expression: it’s more complicated being multicellular
II. The Promoter
V. Alternative splicing
Pancreatic cell Neuron
+ insulin - insulin
- neurotransmitter +neurotransmitter
Levels of Regulation of Eukaryotic Gene Expression
Chromosome structure is continuously rearranged, so that transcriptionally active genes are cycled to edge of territories.
Organization/ packaging of DNA
Nucleus= 5-10 m
Diploid genome= 6.4x109 bp
RNA pol II
Promoters: sequences adjacent to genes, where RNA pol binds to initiate transcription
Euk. - Chromatin and TFs
Prok. - Naked DNA and no TFs needed
“Promoter-Bashing” Mutations Determine the Critical Regions of DNA for Gene Expression
Transcription Regions of DNA for Gene Expression
TBP-TATA binding protein
TAFs- TATA assoc. factors
III. Eukaryotic Enhancers and Promoters Regions of DNA for Gene Expression
Promoters- needed for basal level transcription
Enhancers- needed for full level transcription; location and orientation variable
Two types of transcription factors bind enhancers and affect levels of txn: true activators and anti-repressors
Combinatorial Model of Gene Expression Regions of DNA for Gene Expression
No reg.TFs in this cell for albumin enhancer
Binding of True Activator TFs to Enhancers Greatly Stimulates Transcription
Looping of DNA allows Activator TF bound to Enhancer to interact with Promoter, facilitating binding of Basal TF complex.
Types of Regulatory Transcription Factors Stimulates Transcription
Helix-Turn-Helix (HTH) TFs Stimulates Transcription
(binds operator DNA)
Zinc Finger TFs Stimulates Transcription
Leucine Zipper TFs Stimulates Transcription
Helix-Loop-Helix (HLH) TFs Stimulates Transcription
Antirepressor Transcription Factors Stimulates Transcription
TFs can recruit HATs or HDs Stimulates Transcription
IV. Control of gene expression Stimulates Transcriptionby DNA Methylation
V. Post transcriptional gene regulation Stimulates Transcription
If humans have approximately the same number of genes as a fruit fly, and we require more complex cellular functions (presumably with a larger number of proteins) - how do we accomplish this?
Alternative splicing Stimulates Transcription
1. Chromosomal ratio activates txn of Sxl in females only
2. SXL controls splicing of tra-2 mRNA
3. Females: exon 2 (which has a stop codon) is removed via SXL
Males: exon 2 is not removed.
Males: no active TRA
Females: TRA is made.
5. TRA directs splicing of dsx mRNA in specific manner; in males default splicing occurs.