FINAL EXAM P1 Flashcards
virology
not free-living, must be produced inside the host (intracellular)
not cellular
small genome between 4 - 400
Baltimore classification scheme
based on the nucleic acid content and metabolism of the virus
bacteriophage
viruses that infect bacteria
capsid (capsomere proteins)
a protein coat/capsule that protects the genome of the virus
made via capsomeres
recognizes sites for binding to a new host
can viruses be seen with a microscope
only with an electron microscope
nucleocapsid
a full virus particle
refers to the structure with the nucleic acid and the capsid
envelope
the membrane surrounding the nucleocapsid
formed from a small piece of the cytoplasmic membrane of the cell the virus had infected
what are the stages of the viral life cycle
attachment, penetration, synthesis, assembly/packaging, and release
attachment
aka absorption
the free viral particle attaching to some specific part of the host cell
penetration
aka injection
the genomic nucleic acid getting inside of the host cell
in terms of bacteria, the capsid does not enter the host cell, rather the nucleic acid is injected across the cell wall
synthesis
the virus starts making the parts needed to assemble more viral particles
needs to synthesize nucleic acid for viral proteins by using cellular machinery and subunits
assembly/packaging
putting the nucleic acid inside the capsid
release
aka lysis in case of bacteria
breaks open and releases particles
how is a phage/virus detected
by its ability to infect and kill the bacteria
what is a plaque assay
used for bacteriophage
a plate has host cells forming a lawn. if a bacteriophage is infecting them, plaque will form
what are plaque
clear spots on a bacterial lawn indicating a phage is present
used to quantify data and isolate pure viral strains
how are viruses classified
based on what type of nucleic acid they carry inside and how they replicate it once inside the host cell
double stranded viral DNA
DNA replication works the same way as it does in cells, known as classical semiconservative replication
RNAP makes mRNA to make proteins
dsDNA is fairly simple for viruses
single stranded viral DNA
has an extra step
transcription can only be done with the double strand, so the single strand has to be converted to a double
how is ssDNA converted to dsDNA
first step is to synthesize the complementary strand
the plus strand is already present, so we need the minus strand, simply DNA synthesis
to get back to the ssDNA, the minus strand is a template to make copies of the plus strand
+RNA
same sequence as mRNA
usually ssRNA, as soon as it enters the cell it can start making viral proteins (when used as mRNA)
makes -RNA
-RNA
same is the same as the complementary strand
can’t be used as mRNA
must first use RNA replicase to make a plus strand (mRNA), which is then used to make viable proteins and as a template for more -RNA
makes +RNA
RNA replicase
needed to take RNA and make an RNA copy
one of the first proteins made by mRNA
ssRNA retrovirus
has single stranded +RNA genomes
when entering the host, they’ve brought their own enzyme called reverse transcriptase
reverse transcriptase
takes an RNA template and makes a DNA copy
this is the only organism on Earth that does the opposite, using RNA as a template for DNA
transcription
the process of taking DNA and making RNA copies