BIOL 112 Lecture Notes - Lecture 8: Emtricitabine, Prophage, Darunavir

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9 Apr 2012

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BIOL 112 Full Course Notes

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He tried to figure out the tobacco mosaic virus. Something smaller than a bacteria that reproduces itself; does not dilute like chemicals. Phages have genes and promoters that control the transcription of the genes - a way polymerases know where genes are. Phage rna polymerase to make genes and controls the sequence of the transcribed genes. Make proteins that goes and sit on another promoter that are used to transcribe another gene needed for later to make a new virus and proteins necessary to lyse the cell. Phages can recombine new genomes and produce new genotypes! Only need a few genes to reproduce itself! Animal viruses, just like phage, can undergo recombination . Viruses that like being in lysogenic cycle i. e. hiv/aids , chicken pox/shingles (varicella/zoster) Instead of using rna to be translated directly into new viruses, it creates a dna copy of its rna genome: retroviruses (retro because it makes dna from rna)

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1. There are viruses, called bacteriophage, that infectbacterial cells. Following viral entry, the cell begins tosynthesize viral DNA and viral proteins, leading to the productionof mature virus and the death of the bacterial cell. During thecourse of viral infection, transcription of bacterial genes isturned off so that transcription of viral genes predominates. Whichof the following is the most likely explanation for how the virusmanages to shift transcription from bacterial genes to its owngenes?

a. it synthesizes a viral RNA polymerase that recognizes onlyviral promoters

b. it synthesizes a viral DNA polymerase that recognizes onlyviral origins

c. it synthesizes a viral sigma subunit that directs thebacterial RNA polymerase to viral promoters

d. it has special viral ribosomes that only translate viralproteins

2. Unlike bacterial transcripts, eukaryotic RNA transcripts arechemically modified because:

a. Chemical groups help protect the mRNAs from degradation inthe eukaryotic cytoplasm, bacterial mRNAs are not degraded

b. Chemical groups facilitate the transport of eukaryotic RNAsfrom the nucleus to the cytoplasm, bacterial RNAs are synthesizedin the cytoplasm

c. Eukaryotic RNA polymerases cannot transcribe genes unlessthey are chemically modified, bacterial RNA polymerases transcribeunmodified genes

d. Transcripts in eukaryotic cells contain non coding regionsthat must be removed, bacterial transcripts contain only codingsequence

e. b and d

3. Termination of transcription in both E. coli and eukaryoticcells occurs because

a. there is a termination signal in the DNA following the genesequence.

b. there is a hairpin structure followed by a string of U

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2.)

a.) Are viruses that infect Archaea different from other bacterial viruses?

Yes, they do not have protein coats because of the extreme conditions where they live.

No, they consist of nucleic acid and protein just like other bacterial viruses.

Yes, the structure of archaeal viruses is always completely different from other bacterial viruses.

Yes, they have only DNA genomes.

b.) Of the following examples, which is not a common part of many viral life cycles?

The pox virus genome is replicated by DNA polymerase.

Adenoviruses attach to the cell and the nucleocapsid is taken up by the cell.

Pox viruses replicate in the cytoplasm of the cell.

Once an adenovirus virion is inside a cell, host RNA polymerases transcribe early genes

c.) Some viruses are associated with cancer. There are a variety of ways in which viruses may affect a cell in a way that may lead to cancer. Based on your knowledge of the life cycles of viruses and of molecular genetics, what is one way that this might happen?

Viral genetic material inserts into a host genome close to the termination sequence, far downstream of the promoter, and causes a silent mutation.

Viral genetic material inserts into a host genome in a repetitive noncoding region.

Viral genetic material inserts into a host genome, placing a promoter in a new location and turning on a gene that had previously been turned off.

Viral genetic material inserts into a host genome and causes a mutation in a promoter, turning off a gene that had previously been turned on.

d.) Which statement describes the difference between the normal neuron protein PrP^C and the pathogenic version PrP^Sc?

PrP^C is just a protein and the PrP^Sc is a protein with nucleic acid inside.

The PrP^C protein contains more beta sheets while the PrP^Sc protein contains more alpha helices.

The three-dimensional conformation is identical, but the amino acid sequence is different.

The amino acid sequence is identical, but the three-dimensional conformation is different.

Researchers discovered a new virus and characterized its genome by determining the base composition and the percentage of each base. You want to categorize the virus by its genetic material. Remember that viruses carry their genetic material as DNA or RNA. Given what you know about the structure of the nucleic acids, propose a way to distinguish if the genetic material of this new virus is RNA or DNA, and whether it is single-stranded or doublestranded

BIOL 112 Lecture Notes - Lecture 8: Emtricitabine, Prophage, Darunavir

BIOL 112 Full Course Notes

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