Biochemistry of RNA Flashcards
What are the main components of RNA
usually single stranded
forms loops
ribose/uracil
What is the function of rRNA
combines with proteins to form ribosomes
what is the function of tRNA
carries the amino acids to be added to polypeptide chain
what is the function of mRNA
carries the genetic information (copy of DNA strand from template)
What structures are found on tRNA
anticodon loop
amino-acid attachment site
3’ OH
What enzyme is needed to form RNA
RNA polymerases
How many types of RNA polymerase do eukaryotic cells have
3
What are the steps of transcription
RNA polymerase binding
DNA chain separation
initiation
elongation
termination
What is needed for RNA polymerase to bind
transcription factors
What happens during RNA polymerase binding
ribosomal subunit detects promotors needed to initiate transcription
Why is the DNA chain separated during transcription
to gain access to the nucleotide sequence
What happens when transcription is initiated
First nucleotide to start RNA chain is selected
What is the purpose of elongation
to add more nucleotides to the growing chain of RNA
What happens during termination
finished RNA chain is released
What is the promotor for Polymerase II
TATA box (TBP)
How does a transcription factor alter transcription
determines the start and direction
provides a landing platform for polymerase
How is transcription completed at low basal rates?
Transcription factor (TFIID) remains at the promotor, new initiation complex can assemble
What direction is an RNA chain synthesised in
5’ to 3’
what happens after DNA leaves the transcription bubble
it is rewound
What direction does RNA move ALONG THE DNA TEMPLATE
3’ to 5’, as the RNA chain is made in a 5’ to 3’ direction
How is the finished RNA strand terminated
sequence ends with a series of U’s which are recognised and cleaved by an enzyme
What are specific transcription factors
DNA-binding proteins containing 2 domains
What are the 2 domains of specific transcription factors
DNA-binding domains
transcriptional activation domain
What are enhancers
Sections of DNA activator proteins bind to which enhance the activity of a promotor
Do enhancers have to be directly near a promotor
No
How is gene expression coordinated
stressors activate transcription of a regulatory protein.
This binds to SRE’s, stimulating transcription of specific genes
code for proteins required for response
As introns and exons are transcribed together, how does mRNA not include introns?
Introns are cleaved before translation via splicing
What is the difference between pre-mRNA and mature mRNA
addition of 5’ G cap
Poly A tail
why is the g cap important
Marks RNA as a messenger
important for stability
Why is the poly A tail added
marks end of RNA, stops translation
How is transcription and translation compartmentalised in eukaryotes
Begins in nucleus and ends in cytosol (protein synthesised)
