BCHM 4360 Exam 3 QUESTIONS WITH ACTUAL CORRECT
DETAILED ANSWERS ALREADY GRADED A+
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
DETAILED ANSWERS ALREADY GRADED A+
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
