biochem 7A - RNA structure, syntehsis, and processing Flashcards
Which RNA
-smallest (4S) of the 3 major types of RNA
-at least one specific type of tRNA for each of the 20 aa
-comprise about 15% of RNA in cell
-carries its amino acid on 3’ end, to the site of protein synthesis
transfer RNA
messenger RNA function
-carries genetic information from the nuclear DNA to cytosol, where it is used as the template for protein synthesis
has a long sequence of adenine nucleotides (poly A tail) on the 3’ end and also a cap on the 5’ end consisting of a molecule of 7-methylguanosine attached via triphosphate linkage
messenger RNA
what is the multisubunit enzyme that recognizes a nucleotide sequence (promoter) at the beginning of the length of DNA to be transcribed
RNA polymerase
sense strand / coding strand
DNA strand w the same sequence as the mRNA
antisense strand
DNA strand that is being transcribed into mRNA
what direction does prokaryotic transcription happen
5’-3’
does RNA polymerase need a primer?
no
what direction does the RNA strand grow
5’-3’
the RNA polymerase proceeds along which DNA strand
anti-sense strand
Rho independent termination
stem loop structure signals release of mRNA
rho dependent termination
mRNA pulled away from RNA polymerase
actively transcribed genes are found in what form of chromatin
relaxed form (euchromatin)
most inactive segments of transcribed genes are found in what form of chromatin
condensed form (heterochromatin)
what is chromatin remodeling
when chromatin changes from the relaxed form to the condensed form vise versa
what is a major mechanism of remodeling
acetylation of lysine residues
what catalyzes acetylation
histone acetyltransferases (HAT)
what catalyzes deacetylation
histone deacetylases (HDAC)
RNA polymerase I
synthesize the precursor of the 5.8S, 18S, and 28S rRNA in the nucleolus
RNA polymerase II
syntehsize mRNA
RNA polyermase III
synthesize tRNA and 5S rRNA
mitochondrial RNA polymerase
transcribes RNA from all mitochondrial genes
RNA processing in prokaryotes vs eukaryotes
in prokaryotes - RNA is used as unaltered primary transcript as soon as it is made
in eukaryotes - capping at 5’ end, addition of poly(A) tail at 3’ end, removal of introns
what happens in RNA capping and reason
7-methylguanosine cap at the 5’ end of the mRNA linked to the 5’ ribose via triphosphate linkage
cap protects the 5’ end from exonucleases and promotes mRNA translation by ribosomes
addition of poly-A-tail reason
-40-200 adenine nucleotides attached to 3’ end
-not transcribed from DNA but added after transcription
-helps to stabilize the mRNA
-facilitates the mRNA exit from nucleus and aid in translation
-gradually shortened after entering the cytosol
what catalyzes the addition of poly-A-tail
polyadenylate polymerase
