T3- M3&4 Flashcards
What did all cells derive from
Fertilized eggs
What determines a cell’s fate
Which genes are turned on/off
Why are signals important
To control gene expression
Define proteome
The complete set of proteins made by an organism
What are transcription factors
Proteins which bind to specific DNA sequences
Why are transcription factors essential
- Determine pathway for cell type
- Work with other proteins that result in gene expression changes
How are transcriptional regulation in prokaryotes and eukaryotes similar
- Both activate and repress transcription
- both use RNA polymerase to bind to promotors
How are the DNA in eukaryotes and why
Highly compact chromatin- easy way to fit DNA in nucleus
What do chromatin do
Allow DNA to move around in cell divison
Are genes in tight chromatin expressed?
No, need to unwind
What is DNA wrapped around
Histone proteins
How many histone proteins does each nucleosome have
8 with 150 base pairs
What is chromatin remodelling
The rearrangement of chromatin from a condensed state to a transcriptionally accessible state
What is needed for chromatin remodelling
Activator protein or transcription factor
How is DNA tightly bound
Due to positive tails of histones and negatively charged phosphate in DNA
What is the activator protein recruited for histone modifications
Coactivator enzyme histone acetyltransferase
What does coactivator enzyme histone acetyltransferase do
Attaches acetyl groups to lysine amino acids along positive tails of nucleosome histone proteins
What happens once positive tails are acetylated
Positive charge is reduced and interactions between histones and DNA reduced
What other modifications assist in transcription initiation
Methylation of lysine and arginine
Phosphorylaton of serine and theanine
4 types of transcription factor proteins
- include basic helix loop helix
- helix turn helix
- zinc finger
- leucine zipper
What bonds are between alpha helical domains
Hydrogen bonds
What is the promotor sequence in eukaryotes
TATA box
What is a core promotor
A binding site for RNA polymerase and other transcription factors
What is recognized by TATA box
TATA binding protein or TBP subunit of transcription factor TF2D
What is the BRE region
Promoter for eukaryotes
What is BRE region bound by
TF2B factor
What are enhancer regions
Bind cell or region specific transcription factors
- facilitates formation of transcriptional complex
Where are enhancer sequences in eukaryotes
Distant from promotor
What happens once transcriptional components bound
Flexible DNA allows factors and RNA poly to loop