BIOL 142 Lecture Notes - Lecture 17: Assortative Mating, Chromatin, Genetic Drift

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3 Jul 2018
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Tuesday, April 24, 2018
BIOL 142
Transcription is controlled by the interaction regulatory proteins with variable
regulatory elements"
Methylation of DNA leads to the close state"
Acetylation of histone proteins (tails) leads to the open state"
Dynamic switch between methylation and acetylation"
All eukaryotic promoters are bound by TATA-binding protein (TBP) at the TATA box.
The promoter occurs at the beginning of the gene and is. the site where RNA
polymerase begins transcription"
Promoter-proximal elements are located just upstream of the promoter and the
transcription start site and have sequences unique to specific genes"
Promoter has sequence that is common to most genes"
Promoter-proximal element has sequence that is unique to this gene"
Introns are not necessarily junk, they just don’t code for protein"
Enhancers can be located more than 100,000 bases away from the promoter, in
intron, or in untranscribed 5’ to 3’ flanking sequences. Dierent enhancers are
associated with dierent genes"
Activator proteins bind enhancers an strongly stimulate the transcription complex"
Silencers, negative control elements, repress rather than activate gene expression.
Silencers bind proteins called repressors and turn o transcription - they have the
opposite eect of enhancers"
Silencers (in eukaryotes) work like operators (in prokaryotes) in that they bind
repressors"
Main basal transcription factor that you need - RNA polymerase"
Dierent cell types express dierent genes because they contain dierent regulatory
proteins"
Activation of specific regulatory proteins by extracellular signals leads to proteins
being produced only in certain types of cells"
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