1. There are viruses, called bacteriophage, that infect bacterial cells. Followi
ID: 40688 • Letter: 1
Question
1. There are viruses, called bacteriophage, that infect bacterial cells. Following viral entry, the cell begins to synthesize viral DNA and viral proteins, leading to the production of mature virus and the death of the bacterial cell. During the course of viral infection, transcription of bacterial genes is turned off so that transcription of viral genes predominates. Which of the following is the most likely explanation for how the virus manages to shift transcription from bacterial genes to its own genes?
a. it synthesizes a viral RNA polymerase that recognizes only viral promoters
b. it synthesizes a viral DNA polymerase that recognizes only viral origins
c. it synthesizes a viral sigma subunit that directs the bacterial RNA polymerase to viral promoters
d. it has special viral ribosomes that only translate viral proteins
2. Unlike bacterial transcripts, eukaryotic RNA transcripts are chemically modified because:
a. Chemical groups help protect the mRNAs from degradation in the eukaryotic cytoplasm, bacterial mRNAs are not degraded
b. Chemical groups facilitate the transport of eukaryotic RNAs from the nucleus to the cytoplasm, bacterial RNAs are synthesized in the cytoplasm
c. Eukaryotic RNA polymerases cannot transcribe genes unless they are chemically modified, bacterial RNA polymerases transcribe unmodified genes
d. Transcripts in eukaryotic cells contain non coding regions that must be removed, bacterial transcripts contain only coding sequence
e. b and d
3. Termination of transcription in both E. coli and eukaryotic cells occurs because
a. there is a termination signal in the DNA following the gene sequence.
b. there is a hairpin structure followed by a string of U
Explanation / Answer
1. C
2. e
3. e
4. c
5. a
6. b
7. a,c,e
8. e
9. f
10. a and c
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