Chapter 19: Viruses Flashcards
An infectious particle consisting of genes packaged in a protein coat
Virus
T/F: viruses are more complex in structure than prokaryotic cells
F: much simpler
T/F: Viruses cannot reproduce or carry out metabolism outside of a host cell
T: They are dependent on the host cell
T/F: Viruses are cells
F: Viruses are not cells; they are very small infectious particles
What do viruses consist of?
Nucleic acid enclosed in a protein coat, and some cases, a membranous envelope
Viral genomes consist of which 2 things?
Double/single stranded DNA or double/single stranded RNA
Viruses are classified as which two kinds of viruses?
DNA or RNA
A genome can be what two kinds of shapes of single molecule of nucleic acid?
Linear or circular
How many genes do viruses have in their genome?
Between 3 and 2,000
The protein shell that encloses the viral genome
Capsid
Capsids are built from protein subunits called _______
Capsomeres
What are the two types of main structures of viruses that are associated with capsid?
Helical or icosahedral
Accessory structures that help viruses infect hosts
Protein spikes
Derived from membranes of host cells and surround the capsids of influenza viruses and many other viruses found in animals
Viral envelopes
Contain a combination of viral and host cell molecules
Viral envelopes
Viruses that infect bacteria; AKA “Phages”
Bacteriophages
Have elongated capsid head that encloses their DNA
Bacteriophages
T/F: Viruses replicate only in host cells
T: viruses are obligate I trace lunar parasites; can replicate only within a host cell
A limited number of host species that can infect
Host range
How does a viruses replicate?
Utilizes the cell’s machinery to reproduce
What are the best understood of all viruses?
Phages
What are phage’s two alternative reproductive mechanisms?
Lytic and lysogenic cycle
A phage replicative cycle that culminates in the death of the host cell
Lytic cycle
Produces new phages and lyses (breaks open) the host’s cell wall, releasing the progeny virus
Lytic cycle
Phage that reproduces only by the Lytic cycle is
Virulent phage
Replicates the phage genome without destroying the host
Lysogenic cycle
Viral DNA molecule is incorporated into the host cells chromosome
Lysogenic cycle
Phage that use both the Lytic and lysogenic cycle are called
Temperate phages
The temperate phage that is widely used in biological research
Lambda
Integrated viral DNA
Prophage
What can trigger the virus genome to exit the bacterial chromosome and switch to the Lytic mode?
Environmental signal
Have their own defenses against phages
Bacteria
Foreign DNA can be identified as such and cut up by cellular enzymes called
Restriction enzymes
Both bacteria and archaea can protect themselves from viral infection with what system?
CRISPR-Cas
What does CRISPRs stand for?
Clustered regularly interspaced short palindromic repeats
What are the 2 key variables used to classify viruses that infect animals?
an RNA or DNA genome, either single-stranded or double-stranded; presence or absence of a membranous envelope
Use reverse transcriptase to copy their RNA genome into DNA
Retroviruses
What is the retrovirus that causes AIDS?
HIV (Human Immunodeficiency virus)
Viral DNA that is integrated into the host genomes
Provirus
Unlike a prophage, remains a permanent resident of the host cell
Provirus
What transcribes the pro viral DNA into RNA molecules?
RNA polymerase
Name 3 mobile genetic elements
Plasmids, transposons, and viruses
Smaller, less complex entities that cause disease in animals
Prions
A harmless derivative of a pathogen that stimulates the immune system to mount defense against the harmful pathogen
Vaccine
T/F: viral infections cannot be treated by antibiotics
T
Widespread outbreak
Epidemic
Plant viruses spread disease by 2 major routes
Horizontal and vertical transmission
Entering through damaged cell walls
Horizontal transmission
Inheriting the virus from a parent
Vertical transmission
Infectious proteins that appear to cause degenerative brain disease in animals
Prions
Scrapie in sheep
Prions
Mad cow disease
Prions
Creutzfeldt-Jakob disease
Prions
Incorrectly folded proteins, can be transmitted in food, act slowly, and are virtually indestructible
Prions
Able to convert a normal form of a protein into the misfiled version
Prion
Alzheimer’s and Parkinson’s
Prions
