Biochemistry : Regulating Transcription
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Example Questions
Example Question #51 : Nucleic Acid Synthesis
How does RNA polymerase know when to end transcription of a gene?
It reaches a poly A tail
It reaches an uncodeable segment of the DNA
It synthesizes a termination sequence
It reaches the TATA box
It reaches the Hogness box
It synthesizes a termination sequence
RNA polymerase travels down DNA beginning at the promoter site (could be TATA box or Hogness box in eukaryotes). It reads the DNA and synthesizes mRNA along the way, until it reaches a point where it reads the DNA and synthesizes a termination sequence. This notifies the RNA polymerase that it should end transcription of the gene.
Example Question #52 : Nucleic Acid Synthesis
Spliceosomes must be able to recognize where to splice mRNA so that introns are correctly cut out. What sequence is nearly always conserved in introns to ensure proper splicing?
(Splice) GU----------purines--AG (splice)
(Splice) GU-------pyrimidine--AG (splice)
(Splice) AG-----------purines--GU (splice)
None of these
(Splice) AG----------pyrimidines--GU (splice)
(Splice) GU-------pyrimidine--AG (splice)
Spliceosomes recognize the conserved sequence, GU, and splice just before those two nucleotides. They then continue onwards and when they recognize a pyrimidine followed by the nucleotides, AG, they splice again immediately after the AG. This is almost always conserved in introns to ensure proper splicing.
Example Question #54 : Nucleic Acid Synthesis
Which of the following is/are true regarding prokaryotic RNA polymerases?
I. RNA polymerase requires the sigma protein factor to initiate transcription.
II. Prokaryotes have multiple types of RNA polymerase.
III. RNA polymerase requires the rho protein factor to terminate transcription.
IV. Sigma protein is not required for RNA polymerase to initiate transcription in prokaryotes.
I and IV
I, II, and III
II, III, and IV
I and II
I and III
I and III
There are few differences between prokaryotes and eukaryotes in what concerns transcription. In prokaryotes there is only one RNA polymerase, while in eukaryotes there are three: I , II and III. In prokaryotes, both sigma factor and rho factor are required for transcription to occur, but not in eukaryotes.
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