exam 2 (RNA processing) Flashcards
how do eukaryotes and prokaryotes differ in translation
prokaryotes are translated as its transcribed
eukaryotes aren’t ready to be translated right after being transcribed, and have spacial separation
for eukaryotes, where does transcription and translation occur
transcription = nucleus translation = cytoplasm
for prokaryotes, where does transcription and translation occur
together in the cell
how does newly synthesized RNA and mature mRNA differ in size
newly synthesized RNA is ~10x longer
what is pre-mRNA
hnRNA, newly synthesized RNA
mRNA and hnRNA are digested by what
ribonucleases
in an RNA sequence, T, RNase digests what
G’s
in a RNA sequence, Pancreatic RNase digests what
U’s and C’s
mRNA and hnRNA have ends with a lot of A’s. why?
they are 3’ poly(A) tails
found in most eukaryotes
what are the exception to all eukaryotic mRNAs having poly(A) tails
histone genes
how do humans and yeast compare in their formed poly(A) tails
humans are a lot longer than yeast
how are mRNA’s capped at their 5’ end
7-methylguanosine cap is put on to prevent it from growing (5’-m7G)
must be 20-30 nt long
phosphoryation of the RNAPII CTD
what is the function of the 5’-m7G cap
-protect mRNA from digestion by 5’ –> 3’ exonucleases
-influence RNA export and processing
-translation
-
how is hnRNA converted to mRNA
by removing internal parts of hnRNA sequences
how were split genes discovered
studied viral DNA from infected human cells. There was formed hybrids between viral DNA and late mRNA
exon
transcribed region that encodes amino acids
intron
transcribed sequence between exons that doesn’t encode amino acids
what is splicing and how often does it occur
allows cells to pick the exons they want to use for their mature mRNA
>95%
what is exon skipping
skipping the cassette exon that is in between 2 constitutive exons
what is mutually exclusive exons
one of the 2 middle exons are skipped
what is intron retention
when introns that are normally spliced out remain in sequence
alternative splicing
alternative spicing sites allow different pieces of the same exon to be included or excluded
how are lariat structures formed during splicing
-OH substituents make attacks on on exons, joining exons 1 and 2 together
when does splicing occur
when mRNA is transcribed
CPSF function
binds poly(A) signal and is required for cleavage and polyadenylation
poly(A) polymerase function
Adds as to the 3’ end of the mRNA and is also required for cleavage
RNAPII CTD function
binds to CPSF and is required for cleavage
what is RNA editing
allows a cell to recode genetic information, prior to translation of a mRNA, certain nucleotides can be changed
what letter nucleotide associates with inosine in mRNA and tRNA
A
roles of polyadenylation
transcription termination \
export of mRNA from nucleus to cytoplasm
