EXAM 3- Ch. 7 RNA PROCESSING Flashcards
what components are required for eukaryotic mRNA processing
- 5’ cap
- 3’ poly A tail
- rna splicing
true or false: most rna’s must be further processed before they can carry out their roles
true
any modification made to rna between its transcription and its final function in the cell. term?
rna processing
can prokaryotes or eukaryotes translate mRNA as soon as it is transcribed by rna polymerase
prokaryotes
what is a consequence of prokaryotes translating mRNA as soon as it is transcribed
very little processing of prokaryotic mRNA
true or false: both eukaryote and prokaryotes process their rRNA and tRNA in different ways
false
during prokaryotic processing is mRNA processed
no
multiple genes transcribed on one transcript. term?
operon
transcription unit of prokaryotic processing
operon
what kind of proteins are translated from mRNA in prokaryotes
individual
during eukaryotic processing what is produced
- mRNA
- tRNA
- rRNA
one gene transcribed on one transcript. term?
monocystronic
where does eukaryotic processing occur
nucleus
what does UTR stand for
untranslated region
what is the 1st modification in mRNA processing eukaryote
5’ rna capping
what makes the 3’ end poly a tail
rna processing enzymes
RNA splicing function eukaryote
removes intron sequences from newly transcribed pre-mRNA
what signals where splicing occurs in eukaryotes
nucleotide sequences
what does the splicing in eukaryotes
spliceosome
how does the spliceosome work
uses atp hydrolysis to produce a complex series of RNA-RNA rearrangements
what splices a small fraction of intron sequences in animals and plants
snRNPs
what is selectively exported from the nucleus eukaryote
mature mRNAs
what does the nucleus produce
ribosomes
where will rRNA be edited
Nucleus
modified guanine with methyl group by the formations the triphosphate bridge
5’ cap
what adds the 5’ cap
capping enzymes
what are the 4 functions of the 5’ cap
- ID 5’ end mRNA
- protect from exonuclease
- assist in export
- assist in binging to ribosome
what are the 2 capping enzymes activities
- phosphatase
- methyl transferase
about how many adenines get added to the 3’ end by 3’ poly A tail
200
location of 3’ poly A tail
around 30 nucleotides from cleavage signal
is a template needed for 3’ poly A tail
no
2 functions of 3’ poly A tail
- assisted in export out of nucleus
- protects against degradation by exonuclease
def: the removal of introns from pre-mRNA and join of exons to form mRNA
splicing
what 3 things are required for splicing
- splisosome
- consensus sequences
- ATP
what do consensus sequences mean
similar in all species
true or false: rna has catalytic activity
true
what is the splicesosome made of
large complex of snRNPs
in the splicesosome what recognizes consensus sequences on pre-mRNA
U1 and U2
in the splicesosome what binds consensus sequences on pre-mRNA
U4, U5, U6
rna- rna =
- confirms splice site
- check splicing accuracy
what occurs in splicing rxn
- exchange of 2 alcohol groups in 2 transesterification rxn
in an transesterification rxn (1) what does the branch point react with
5’ of intron
in an transesterification rxn (1) what bonds are broken
phosphodiester
in an transesterification rxn (1) the intron end covalently binds to what
a branch
in an transesterification rxn (2) what does the 3’ end of first exon react with
5’ end of second exon
what forms at the end of a transesterification rxn
lariat
what kind of modifications are in tRNA
chemical changes
rRNA maturation requires
- cleavage and chemical modification
what does the mature mRNA have to bind to for export to the cytoplasm
proteins/ nuclear transport receptors
where and how does the mature mRNA come out of
nuclear pore complex
active transport
what life on earth was before DNA
pre-RNA
in eukaryotes what is the advantage of non coding sequences
alternative splicing
what % are exons in DNA
1%
what % are introns in DNA
20%
what are the advantages of alternative splicing
- producing different proteins from a single gene
- more proteins
- specific proteins
