CSB351Y1 Lecture Notes - Lecture 2: Oncogene, Parasitism, Orthomyxoviridae

131 views2 pages
user avatar
Published on 4 Apr 2011
School
UTSG
Department
Cell and Systems Biology
Course
CSB351Y1
Definition of Virus
Viral particles formed of one or several molecules of nucleic acids: RNA OR DNA, but never both
{
Virus: icosahedral or helical shaped (RNA not in the hole of the loop but is packed inside the helix
{
Capsid/coat is to protect virus: most viruses have capsid --> some viruses may exist without
{
Some viruses are parasite of other viruses: Hep D (human) is parasite of HepB --> steals capsid protein
{
Virus, consisting of genetic material enclosed in a protective coating
¾
¾
No metabolic system, no intrinsic motility, cannot respond to stimuli, do not grow in the usual sense--> EXCEPTION: one
bacteria virus (tail part contracts, virus injects DNA into bacteria)
¾
Ability to maintain genetic continuity, with possibility for mutation, is the only basis for considering viruses to be ALIVE
¾
Viruses: in ever single living organism--> ubiquitous
¾
HIV: retrovirus--> different: take their genetic info (RNA), convert into DNA, which goes into nucleus of the cell,
integrate into chromosome and stay there --> viral genetic information becomes a PART of genetic info of the cell
|
All other types: don't go near the nucleus--> go into cytoplasm of the cell, makes millions of copies of their own
gene then virus particle and then burst through the cell
|
Virus integrates piece of DNA near oncogene (normal genes in human cells involved in cell division--> most of
these, proto-oncogenes,usually turned off after embryonic stage)--> viral DNA integration re-activate oncogene-->
continuous/unstoppable cell division--> cancer (i.e. Cervix cancer)
|
The genes added to cell by the virus cause the infected cell to either produce more virus particles (end result cell death)
or to change characteristics of the cell (cancerous)
¾
Goodheart (1969):
{
Nature of Virus
Particles formed of one or several molecules of nucleic acids: RNA or DNA but not both
{
Several= Divided genome--> i.e. Influenza virus (several pieces of RNA)
One= single genome--> i.e. Polio, TMV
CAPSID: genome usually (but not necessarily) covered by one or several types of protein
{
Envelope: some viruses, on top of having capsid protein, also have envelope
{
Polio virus, Norwalk
¾
Most ___ plant viruses are not enveloped
¾
Enveloped: HIV, Herpes, Rabis
¾
Not all viruses are enveloped:
Influenza virus: i.e. H1N1
¾
HA = glycoprotein (protein + sugar attached) --> used as receptor-binding for the virus: recognize some molecule (sialic
acid) on the surface of the cell to ATTACH--> virus is endocytosed by the cell --> replicates in the cell, makes lots of
copies, infection--> virumia= lots of virus in the blood--> FEVER: immune system makes Ab
NA = neuraminidase --> exactly like sialic acid, but functions to cut virus and release them from the cell, so they can go
and infect other cells
Virus: before get released from cell, spike into their lipid bilayer the VIRAL NA and HA --> virus then detach and signal
LIPID: viruses take it from the cell they infect --> through budding
Smaller: bacteria 1 micron, viruses 30 000 to make up 1mm
¾
Simpler
¾
Unable to multiply outside a living cell --> Absolute Parasitism
¾
Viruses are:
{
Nucleic acid: RNA/DNA carries genetic information, to code for diff genes of the virus
¾
Genome = set of genes
All viruses must code for at least 1 protein: polymerase (few exceptions) --> synthesis of new RNA/DNA of the virus; all
also code for their coat/capsid proteins to cover and protect their genetic material + form the virus particle
Here: must take nucleotides from the cell's machinery --> cannot synthesize their own nucleotides
Protein: i.e. TMV only 1 protein making helical structure
¾
Lipids: not all have this
¾
Carbohydrates
¾
Cations: K+1, Ca+2, Mg+2
¾
Nucleic acid = sugar + base + phosphate
RNA/DNA: -charged due to phosphate groups (normally have + charged histones to neutralize this)
Virus: grabs some cations from the cell to neutralize
Composition of viruses:
{
Structure:
{
Sperhical/icosahedral
Helical/rod shaped
Combination
Replication:
{
Lecture 2 Definition of Virus
September-17-09
1:26 PM
CSB351 Course Notes Page 1
www.notesolution.com
Unlock document

This preview shows half of the first page of the document.
Unlock all 2 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Viral particles formed of one or several molecules of nucleic acids: rna or dna, but never both. Virus: icosahedral or helical shaped (rna not in the hole of the loop but is packed inside the helix. Capsid/coat is to protect virus: most viruses have capsid --> some viruses may exist without. Some viruses are parasite of other viruses: hep d (human) is parasite of hepb --> steals capsid protein. Virus, consisting of genetic material enclosed in a protective coating. No metabolic system, no intrinsic motility, cannot respond to stimuli, do not grow in the usual sense --> exception: one bacteria virus (tail part contracts, virus injects dna into bacteria) Ability to maintain genetic continuity, with possibility for mutation, is the only basis for considering viruses to be alive. The genes added to cell by the virus cause the infected cell to either produce more virus particles (end result cell death) or to change characteristics of the cell (cancerous)