CHPT 26: Viruses Flashcards
Why do retroviruses need to contain the enzyme reserve transcriptase?
bc the host cells genomes do no contain a gene encoding an enzyme that can make DNA from RNA
What is the most reasonable for why a bacteriophage is capable of infecting E coli would be unable to infect a human lung epithelial cell?
the receptors to which the bacteriophage attach on E coli are not found on lung cells
Why might the ability of a virus to convert a being bacterium into a pathogen be selected for by natural selection?
the pathogenic virus may cause disease symptoms (diarrhea, coughing) that lead to spreading of the virus
Which of the following kinds of proteins would be least likely to be expressed during the lysogenic cycle of a temperate phage?
a protein to promote cell lysis by breaking down the cell wall of the host cell
Why is a drug that blocks HIV binding to one of its cell surface receptors not effective at treating influenza?
HIV and influenza viruses have different receptors to which they bind
Why is HAART more effective than a single drug in reducing HIV levels in infected people?
mutations that confer resistance to several drugs are much less likely than is a mutation that confers resistance to. single drug
The “information” contained in PrpSc must be contained in
the three dimensional structure of the PrpSc protein
What are viruses?
genetic elements enclosed in protein that can replicate
not organisms
lack cell structures, reproduction, and independent metabolism
Virus Structure
a core nucleic acid (either RNA or DNA) surrounded by protein capsid
no cytoplasm
What are viruses classified by?
Genomes
DNA Virus
RNA Virus
or Retrovirus
What are the two virus reproductive cycles?
Lytic and Lysogenic
Lytic Horizontal Transmission
produce new virus particles in the cell, then it ruptures allowing more virus to attack other cells
Lysogenic Vertical Transmission
through a host cell division by integrating into the host cell genome, its called prophage, and resulting cell is called lysogen
Antigenic Drift
small changes that changes the surface proteins of the virus
result in viruses that differ but are closely related
why people can get the flu more than once and the vax is updated
Antigenic Shift
it is an abrupt change
two or more diff strains of viruses or strains combine to form a new subtype having a mixture of the surface antigens
