VIRUSES Flashcards
what does a typical virus consist of?
nucleic acid
capsid - protein coat
and sometimes an envelope
is it worth for a virus to have an envelope?
yes, an envelope facilitates virus’ penetration of the cell, because it can fuse with a cell’s membrane
lytic cycle
(from lyse = brake)
bacteriophages infect bacteria, by injecting genetic information
the cell makes copies of her DNA, which now contains bacteria’s genetic information
(DNA polymerase), DNA polymerase makes proteins (RNA polymerase and ribosomes involved), once the proteins are produced the cell lyses - viruses erupt the cell and go to another cell to infect it
ONE virus —> many viruses
lysogenic cycle
the cell doesn’t produce bacteria but the virus genetic information is in the cell along with the cell’s genetic information; cell divides
using bacteria as machinery to produce a lot of copies of genetic material
example of a bacteria that undergoes lytic cycle?
chickenpox
example of a bacteria that undergoes lysogenic cycle and then jumps to lytic cycle?
cold sore
are viruses alive?
viruses are not “alive”, but are obligate intracellular parasites that infect all forms of life
can viruses synthesise proteins & ATP?
no, so they have to rely on host mechanisms
Foot and Mouth Disease Virus produces…
in 2001 ____ million animals slaughtered
Cost to tax payer: £_______, aka £____ per every person
lesions
6.24 million
£20 billion
£333
infectious diseases comprise ____%, _____ m deaths worldwide per annum
33%
17.3m
infections are much more common in developing countries - they are ___% time the cause of death, whereas in the developed countries it’s just ___%
46%
1%
virus life cycle:
- ________
- ________
- ___/____
- ________
- ________
- ________
- ________
- ___/____
- ___/____
- recognition
- attachment; as a fusing bubble or on a surface
- fusion (bubble) / penetration (endocytosis)
- uncoating
- transcription
- protein synthesis
- replication
- assembly (putting it together) / envelopment (?)
- lysis & release / budding & release
intracellular virus is ___ (slower/faster) than extracellular one
faster
simple forms of virions (4):
- naked icosahedral capsid
- enveloped icosahedral
- naked helical nucleocapsid
- enveloped helical nucleocapsid
icosahedral capsid looks like _____ and has a symmetry of…
football
Pentons and hexons (5- and 6-fold symmetry)
properties used in taxonomic constructions for viruses (6):
- type of nucleic acid
- strandedness
- linear/circular
- sense
- number of segments
- nucleotide sequence
sense can be (2):
Positive, naked RNA infectious
OR
Negative, naked RNA non-infectious and needs an enzyme to copy RNA
negative-sense RNA means
RNA that is the complement of the mRNA needed for protein translation
positive-sense RNA means
RNA that is ready for translation
examples of negative-sense single-stranded RNA viruses
those that cause measles, mumps, rabies and influenza
examples of positive-sense single-stranded RNA viruses
those that cause polio, hep C and common cold
how do retroviruses work?
4 steps + process/enzyme + significant term
- single stranded (SS) RNA
- -viral reverse transcriptase –> - cDNA
- –replication—> - DS DNA
- –integrase—> - integration of DNA into host’s DNA [in this step the DNA that comes from the virus is called PROVIRUS]
what kind of species can be infected by retroviruses?
vertebrates
what are retroviruses associated with
the development of various forms of cancer, as cells infected with these viruses are likely to undergo uncontrolled replication
example of retrovirus
HIV (human immunodeficiency virus)
