Unit 1: Transcription Flashcards
What is the central dogma ?
A digram showing how info flows from DNA–> RNA—> Proteins
What are the 3 types of RNA polymerases in eukaryotes ?
1) Pol 1
2) Pol 2
3) Pol 3
Where is RNA polymerase pol 1 found ?
In ribosomal RNAs to be used in translation
Where is RNA polymerase pol 2 found ?
In mRNA for translation into proteins
Where is RNA polymerase pol 3 found ?
In small RNAs such as tRNA
What are the 3 steps of RNA synthesis ?
1) Initiation
2) Elongation
3) RNA processing and termination
Transcriptional initiation is a major way of …..?
Regulating gene expression
Free nucleotides are always added at what end ?
The 3’ to 5’
What is the RNA sequence the same as ?
The coding strand
What is the difference between the coding strand and the RNA sequence ?
Uracil is used instead of thymine
What DNA strand is complementary to the RNA sequence ?
The template strand
What is the promoter region responsible for attracting ?
General transcriptional factors- they recognise sequence close to start site
What is the function of TBP (2) ?
- It recognises TATA protein
- Binds to TATA attracting other TFs to form a preinitiation complex
What is needed aswell as general TFs ?
Gene specific TFs
What can gene specific TFs do ?
Can bind at other sequences that are close to promotor sequence
What is the ‘velcro’ model (3) ?
- Model to show roles of TFs
- Multiple places where sequence specific binding proteins are binding to sequence
- Through combination of protein-protein interactions, RNA polymerase 2 is attracted
What are the 2 grooves found in helical DNA called ?
- Major groove
- Minor groove
Where are the major and minor groove located ?
On opposite sides of the helix to one another
What are 4 structural motifs often found in TFs ?
1) Helix-Turn-Helix
2) Zinc finger
3) Leucine zipper
4) Helix-Loop-Helix
What is the structure and function of helix-turn-helix ?
Two alpha helices connected by a short turn, enabling the protein to bind to specific DNA sequences and regulate gene expression
What is the structure and function of zinc finger ?
It is a protein motif that coordinates a zinc ion to stabilize its structure, which enables it to bind specifically to DNA
What is the Leucine zipper ?
It is a protein motif that enables dimerization of transcription factors through hydrophobic interactions between leucine residues
What is the structure and function of helix-loop-helix ?
The motif consists of two alpha helices connected by a flexible loop, and is a protein structure that enables dimerization and DNA binding
What is topoisomerase ?
An enzyme that plays a critical role in the supercoiling and unwinding of DNA during processes like DNA replication, transcription, and repair
What is elongation ?
- Process to make DNA single stranded
- Requires topoisomerase and rudder
How is a 5’ cap added and what is its purpose ?
- A single 7-mythyl guanosine is attached to the first nucleotide by a triphosphate linkage
- This causes the 2 phosphate groups on the 5’ ends to bond to each other
- Protects ends from degradation
- Aids in initiation of protein synthesis
What are SNRAs?
Small nuclear RNAs that are essential components of splicesome
What is splicing ?
When introns are removed from pre-mRNA so that it can become mature mRNA
What is alternative splicing ?
- It is a process that allows a single gene to generate multiple mRNA variants, by selecting different splice sites during pre-mRNA processing
- This increases the diversity of proteins in a cell and allows for more precise regulation of gene expression
