PCB 3134 exam 4 - Questions with Correct Answers
(Verified Update)
32 questions with answers
Topic: PCB 3134 exam 4
1. evidence for triplet codes
Answer: rounds of mutations using proflavininserts or deletes singular nucleotides 1 round:
all proteins made are non-functional 2 rounds: some proteins are non-functional (if 2
insertions or 2 deletions) and some proteins are functional (if 1 insertion and 1 deletion) 3
rounds: most proteins are non-functional, some are functional (if all 3 insertions or all 3
deletions)
2. initiation of bacterial transcription
Answer: sigma subunit of RNA polymerase binds to the -10 (pribnow box) and -35 sequences
alpha subunit of RNA polymerase binds to upstream (UP) elements
3. elongation of bacterial (and eukaryotic) transcription
Answer: DNA is threaded through RNA polymerase. RNA polymerase unwinds the DNA and
adds new nucleotides to the 3' end. After addition, the helix is rewound
4. termination of bacterial transcription
Answer: RNA polymerase copies the termination signal 2 complementary GC regions on RNA
form a hairpin loop complementary AU regions on RNA and DNA break apart, releasing the
RNA molecule
5. how is eukaryotic transcription different from bacterial transcription
Answer: 1. 3 RNA polymerases 2. transcription factorsadditional proteins 3. varied
promoters 4. RNA processing/chemical modification
6. three types of eukaryotic RNA polymerases
Answer: 1 is for rRNA 2 is for mRNA and snRNA 3 is for tRNA and small RNA's
7. types of eukaryotic core promoters
Answer: TATA driven (RNA polymerase 2): has initiator sequence, TATA box, and sometimes
BRE DPE driven (RNA polymerase 2): has initiator sequence and DPE downstream promoters
(RNA polymerase 3): either boxes A and B or boxes A and C
8. initiation of eukaryotic transcription (RNA polymerase 2 only)
Answer: transcription factors bind to promoters to form a preinitiation complex 1. TF2D
binds to the TATA box 2. TS2B binds to BRE (if present) 3. other TF2's bind to each other and
as a result, recruit RNA polymerase 2
9. termination of eukaryotic transcription
Answer: for RNA polymerase 2: transcripts are cleaved by RNAse after the polyadenylation
sequence (10-35 base pairs downstream). then, the poly A tail is added for RNA polymerase
3: similar to bacterial termination. string of U's in the sequence, no proteins required
10. post-transcriptional modification of tRNA
Answer: 1. 5' end cleaved 2. internal sequence removal 3. some nucleotides removed at 3'
end and replaced with CCA 4. some nucleotides modified (ex: methylation)
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(Verified Update)
32 questions with answers
Topic: PCB 3134 exam 4
1. evidence for triplet codes
Answer: rounds of mutations using proflavininserts or deletes singular nucleotides 1 round:
all proteins made are non-functional 2 rounds: some proteins are non-functional (if 2
insertions or 2 deletions) and some proteins are functional (if 1 insertion and 1 deletion) 3
rounds: most proteins are non-functional, some are functional (if all 3 insertions or all 3
deletions)
2. initiation of bacterial transcription
Answer: sigma subunit of RNA polymerase binds to the -10 (pribnow box) and -35 sequences
alpha subunit of RNA polymerase binds to upstream (UP) elements
3. elongation of bacterial (and eukaryotic) transcription
Answer: DNA is threaded through RNA polymerase. RNA polymerase unwinds the DNA and
adds new nucleotides to the 3' end. After addition, the helix is rewound
4. termination of bacterial transcription
Answer: RNA polymerase copies the termination signal 2 complementary GC regions on RNA
form a hairpin loop complementary AU regions on RNA and DNA break apart, releasing the
RNA molecule
5. how is eukaryotic transcription different from bacterial transcription
Answer: 1. 3 RNA polymerases 2. transcription factorsadditional proteins 3. varied
promoters 4. RNA processing/chemical modification
6. three types of eukaryotic RNA polymerases
Answer: 1 is for rRNA 2 is for mRNA and snRNA 3 is for tRNA and small RNA's
7. types of eukaryotic core promoters
Answer: TATA driven (RNA polymerase 2): has initiator sequence, TATA box, and sometimes
BRE DPE driven (RNA polymerase 2): has initiator sequence and DPE downstream promoters
(RNA polymerase 3): either boxes A and B or boxes A and C
8. initiation of eukaryotic transcription (RNA polymerase 2 only)
Answer: transcription factors bind to promoters to form a preinitiation complex 1. TF2D
binds to the TATA box 2. TS2B binds to BRE (if present) 3. other TF2's bind to each other and
as a result, recruit RNA polymerase 2
9. termination of eukaryotic transcription
Answer: for RNA polymerase 2: transcripts are cleaved by RNAse after the polyadenylation
sequence (10-35 base pairs downstream). then, the poly A tail is added for RNA polymerase
3: similar to bacterial termination. string of U's in the sequence, no proteins required
10. post-transcriptional modification of tRNA
Answer: 1. 5' end cleaved 2. internal sequence removal 3. some nucleotides removed at 3'
end and replaced with CCA 4. some nucleotides modified (ex: methylation)
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