BCHM 4360 EXAM 3 185 QUESTIONS & CORRECT
ANSWERS LATEST 2025
What are the three main benefits to RNA processing? - ANSWER-1. Contribution
to regulation of gene activity
2. Diversity - many different RNAs can be produced from one gene via alternative
splicing
3. Quality control
Many of the RNA processing complexes contain both _______ and ___
components. Give an example. - ANSWER-protein, RNA, RNPs
An E. coli precursor encodes __ rRNAs and __ tRNAs. - ANSWER-3, several
The S. cerevisiae precursor encodes __ rRNAs. - ANSWER-3
Why is encoding several RNAs in one precursor beneficial? - ANSWER-ensures
that similar amounts of each RNA are made
True or False: Exonucleases operate strictly in the 3' to 5' direction during RNA
processing. - ANSWER-False, go both ways
Give two examples of endonucleases. - ANSWER-RNase III and RNase P
,5' trimming of tRNAs is done by which endonuclease? - ANSWER-RNase P
True or False: Both the bacterial and eukaryotic RNA component of RNase P can
cut RNA alone - ANSWER-False: Only bacterial can cut alone
True or False: Some rRNA introns can catalyze their own removal and are
subsequently called self-splicing. - ANSWER-True
What is the CCA sequence? - ANSWER-It is the attachment site on the tRNA for
the amino acid
What are the two most common rRNA modifications? - ANSWER-1. ribose 2'-O-
methylation
2. pseudouridylation
True or False: Post-transcriptional chemical modifications are limited to small
additions such as methylation - ANSWER-False: Modifications can be small, like
methylation, but can also be large, like the addition of a threonine
What are snoRNAs and what is their general purpose? - ANSWER-small nucleolar
RNAs typically made from introns of precursor mRNAs and they are typically used
as guide RNAs
Describe how snoRNAs catalyze methylation of nucleotides - ANSWER-The
snoRNA base-pairs with specific regions of target RNAs and directs enzymes to
these positions
,snoRNAs that direct ribose methylation are _______ snoRNAs. snoRNAs that
direct pseudouridylation are ______ snoRNAs. - ANSWER-box C/D, H/ACA
What is the primary purpose of the end modifications of eukaryotic RNAs
following transcription? - ANSWER-protection of mRNAs from nuclease
degradation and assisting with protein interactions
What are the 5' ends of mRNAs capped with? - ANSWER-7-methylguanine
nucleotide via a 5'-5' triphosphate linkage
What is the 5' cap needed for? - ANSWER-efficient elongation and termination of
the transcript, for mRNA processing and export from the nucleus, and for
directing translation
What are the three steps for the addition of the 5' cap? - ANSWER-1. An RNA 5'
triphosphate catalyzes removal of a phosphate from the 5' end
2. A guanyl transferase attaches a guanosine monophosphate (GMP) to the end in
a 5'-5' triphosphate linkage
3. The guanine is methylated by a guanine-7-methyltransferase
The 3' end of most eukaryotic mRNAs have about ___ adenosines added, known
as the poly(A) tail. - ANSWER-200
Polyadenylation at the _______ site retains multiple regulatory sequences.
Polyadenylation at the _______ site eliminates the regulatory sequences. -
ANSWER-distal, proximal
, What are the steps for the addition of the poly(A) tail? - ANSWER-1. Initial
cleavage after a CA that lies between a conserved AAUAAA hexamer and a U or
GU-rich region
2. After cleavage, ~200 adenosines are added by poly(A) polymerase
What is responsible for mediating mRNA processing? - ANSWER-The CTD of the
largest subunit of RNA Pol II, RBP1
__________ is needed to allow RNA Pol II to continue transcription. __________
is needed for efficient transcription termination. - ANSWER-Capping,
polyadenylation
How does the CTD of RBP1 sequentially recruit the different processing
complexes? - ANSWER-1. CTD becomes partially phosphorylated on transcription
initiation and recruits capping enzyme
2. Elongation leads to more phosphorylation of CTD, which recruits splicing
machinery
3. This also leads to recruitment of the cleavage and polyadenylation complex
True or False: Transcription, processing, and translation all occur in the nucleus. -
ANSWER-False: Transcription and processing occur in the nucleus, but translation
occurs in the cytoplasm so mature mRNAs must be exported from the nucleus
What determines when the RNA-protein complex can be released from the
transcription complex for export to the cytoplasm? - ANSWER-Protein factors
needed for transport are loaded onto the mRNA during transcription, but
polyadenylation is what is mainly needed
ANSWERS LATEST 2025
What are the three main benefits to RNA processing? - ANSWER-1. Contribution
to regulation of gene activity
2. Diversity - many different RNAs can be produced from one gene via alternative
splicing
3. Quality control
Many of the RNA processing complexes contain both _______ and ___
components. Give an example. - ANSWER-protein, RNA, RNPs
An E. coli precursor encodes __ rRNAs and __ tRNAs. - ANSWER-3, several
The S. cerevisiae precursor encodes __ rRNAs. - ANSWER-3
Why is encoding several RNAs in one precursor beneficial? - ANSWER-ensures
that similar amounts of each RNA are made
True or False: Exonucleases operate strictly in the 3' to 5' direction during RNA
processing. - ANSWER-False, go both ways
Give two examples of endonucleases. - ANSWER-RNase III and RNase P
,5' trimming of tRNAs is done by which endonuclease? - ANSWER-RNase P
True or False: Both the bacterial and eukaryotic RNA component of RNase P can
cut RNA alone - ANSWER-False: Only bacterial can cut alone
True or False: Some rRNA introns can catalyze their own removal and are
subsequently called self-splicing. - ANSWER-True
What is the CCA sequence? - ANSWER-It is the attachment site on the tRNA for
the amino acid
What are the two most common rRNA modifications? - ANSWER-1. ribose 2'-O-
methylation
2. pseudouridylation
True or False: Post-transcriptional chemical modifications are limited to small
additions such as methylation - ANSWER-False: Modifications can be small, like
methylation, but can also be large, like the addition of a threonine
What are snoRNAs and what is their general purpose? - ANSWER-small nucleolar
RNAs typically made from introns of precursor mRNAs and they are typically used
as guide RNAs
Describe how snoRNAs catalyze methylation of nucleotides - ANSWER-The
snoRNA base-pairs with specific regions of target RNAs and directs enzymes to
these positions
,snoRNAs that direct ribose methylation are _______ snoRNAs. snoRNAs that
direct pseudouridylation are ______ snoRNAs. - ANSWER-box C/D, H/ACA
What is the primary purpose of the end modifications of eukaryotic RNAs
following transcription? - ANSWER-protection of mRNAs from nuclease
degradation and assisting with protein interactions
What are the 5' ends of mRNAs capped with? - ANSWER-7-methylguanine
nucleotide via a 5'-5' triphosphate linkage
What is the 5' cap needed for? - ANSWER-efficient elongation and termination of
the transcript, for mRNA processing and export from the nucleus, and for
directing translation
What are the three steps for the addition of the 5' cap? - ANSWER-1. An RNA 5'
triphosphate catalyzes removal of a phosphate from the 5' end
2. A guanyl transferase attaches a guanosine monophosphate (GMP) to the end in
a 5'-5' triphosphate linkage
3. The guanine is methylated by a guanine-7-methyltransferase
The 3' end of most eukaryotic mRNAs have about ___ adenosines added, known
as the poly(A) tail. - ANSWER-200
Polyadenylation at the _______ site retains multiple regulatory sequences.
Polyadenylation at the _______ site eliminates the regulatory sequences. -
ANSWER-distal, proximal
, What are the steps for the addition of the poly(A) tail? - ANSWER-1. Initial
cleavage after a CA that lies between a conserved AAUAAA hexamer and a U or
GU-rich region
2. After cleavage, ~200 adenosines are added by poly(A) polymerase
What is responsible for mediating mRNA processing? - ANSWER-The CTD of the
largest subunit of RNA Pol II, RBP1
__________ is needed to allow RNA Pol II to continue transcription. __________
is needed for efficient transcription termination. - ANSWER-Capping,
polyadenylation
How does the CTD of RBP1 sequentially recruit the different processing
complexes? - ANSWER-1. CTD becomes partially phosphorylated on transcription
initiation and recruits capping enzyme
2. Elongation leads to more phosphorylation of CTD, which recruits splicing
machinery
3. This also leads to recruitment of the cleavage and polyadenylation complex
True or False: Transcription, processing, and translation all occur in the nucleus. -
ANSWER-False: Transcription and processing occur in the nucleus, but translation
occurs in the cytoplasm so mature mRNAs must be exported from the nucleus
What determines when the RNA-protein complex can be released from the
transcription complex for export to the cytoplasm? - ANSWER-Protein factors
needed for transport are loaded onto the mRNA during transcription, but
polyadenylation is what is mainly needed
