RNA Metabolism I -RNA synthesis 25 done Flashcards
What are mRNAs?
messenger RNA encodes the amino acid sequence of all polypeptides found in the cell
What are tRNAs?
transfer RNAs match specific amino acids to triplet codons in mRNA during protein synthesis
What are rRNAs?
ribosomal RNAs are ribosome constituents and facilitate catalysis during translation
What are miRNAs?
they regulate the expression of genes in eukaryotic nucleotide sequences
What is the genomic material of viruses?
RNA
What is transcription?
It is when ribonucleic acids are synthesized from DNA in a cell
What RNA single or double stranded? What is the benefit?
single. means they can fold into compact structures with specific functions
What are ribozymes?
RNA molecules that act as catalysts. THey may use metal ions as a cofactpr
Where does RNA polymerase bind to begin transcription?
Binds to a segment of DNA called the promoter. This doesn’t require a primer
What events or what does RNA polymerase form after it binds to the promoter site?
It causes a hybrid of RNA and DNA base-pair bounding of about 8bp. This is netween the new RNA strand and the template strand of DNA This area of DNA will then unwind, forming a buble of about 17 bp. Ahead of the bubble are positive supercoils (overwound). Behind the bubble are negative supercoils (underwound)
What is the role of topoisomerase?
It will eliminate the positive supercoils.
What are the similarities between replication and transcription?
They both require one single strand of DNA as a molecular template for building the new strand
- both add nucleotides via attack of 3’ hydroxyl of the growing chain to a-phosphorus of nucleoside triphosphate. RNA synthesis requires a nucleoside triphosphate, while replication gets away with a nucleotide. ALso, RNA pairs A=U not dA=dT
- both require catalysis by a Mg2+ dependent enzyme
What is the DNA template strand? What is the DNA nontemplate strand?
Template - It is the template for RNA polymerase. It is the 3’ end of the OG Dna strand so that the appropiate RNA transcript can be synthesized
Nontempalte- It is considered the non-coding strand. It has the same sequence as the newly synthesized RNA strand, just the U=T
What is adenovirus? Why is it important?
It is one causative agent of common cold. It is important, because it shows that both DNa strands can be used to encode proteins, rather than just the DNA templete strand.. It has a linear genome
What is a holoenyme?
consistsnt of protein part of enzyme and cofactor
Why are errors okay for RNA polymerase?
They are okay because although RNA pol lacks 3’ -> 5’ -exonuclease, it is transient
What is the a-subunit of RNA polymerase?
assembly and binding to UP elements
What is the B-subunit of RNA Pol?
main catalytic subunit
What is the B’-subunit of RNA POl
responsible for DNA binding
What is the w subunit of RNA Pol?
protects pol from denaturation
What is the sigma-subunit?
directs enzyme to promoter, starting trancription process
Describe the structure of RNA Polymerase promoters
HAve TATA sequences about 10 base pairs betfore transcription start because the allows for easier strand separtion during initiation
What is the closed complex?
DNa is bound to RNA polymerase, but not unwound
What is the open complex?
WHen RNA polymerase is bound to DNA promoter site. The two chains a=in AT rich promoter site are separated
WHen does RNA polymerase sigma submit leave?
before elongation. ONly stays for initiation
WHen RNA pol moves from promoter, what replaces the sigma subunit?
protein NuSA. This maintains processivity
What is p-independent?
Releases mRNA from the RNA-DNA hybrid by hairpining on itself. This causes it be released from the templete. The hairpin system has lots of UUUs at 3’ end of
What is p-dependent?
Why to terminate transcription. The p-helicase will bond to the rut site of the synthesisng RNA strand. Rut site can be anywhere on the strand. WHen it binds, it will travel up the strand until it reaches the termination site, where it separates mRNA from templete strand
