Exam 1 Chapter 21 Viruses Flashcards
capsid
outer layer of virus composed of proteins subunits.
Protein on surface can interact with a protein on surface of host cell.
Nucleic Acid Core
Inner most portion is made of DNA or RNA
envelope
possessed by some viruses.
are a lipid membrane that is rich in lipoprotein and glycoproteins surrounding virus capsid.
spike
glycoproteins that project from some enveloped viruses allowing for attachment of the virus to the targeted host cell.
Virus
intracellular parasites. Do not possess cell.
Are essentially chemical complexes of RNA or DNA protected by protein.
Virus shapes
Helical: usually plant viruses
Icosahedral: usually animal viruses
Complex binary: bacteria viruses
Viral reproduction
1) attachment
2) penetration
3) biosynthesis (assembly)
4) maturation
5) release
1) entry into host because portions of capsid adhere to specific receptor on host cell’s outer surface.
2) Viral nucleic acid enter host cell and codes for protein units inside capsid
3) virus takes over metabolic machinery of host cell
host range
usually limited host range
tissue tropism
targeting of specific range of cells within suitable organism
transformation
genetic alteration of a cell’s genome by the introduction of foreign DNA
latent virus
virus that is able to hide from host’s immune system by integrating itself into host cell’s genome and not producing new viruses (ex: chicken pox and HIV)
retrovirus
have the enzyme reverse transcriptase.
high error rate of reverse transcriptase leads to high genetic diversity of HIV: this in turns creates difficulty in creation of vaccine.
direction of genetic information transfer in a retrovirus is RNA to DNA to mRNA to protein. (ex: HIV)
bacteriophage
virus that infects bacteria
virulent virus
causes lysis of their hosts.
emergent virus
virus in a new host with a potential lethality rate of 50% (EBOLA) can jump from one species to another.
viroids
tiny, naked molecules of RNA a few hundred nucleotides long whose sequence resembles intron sequences in rRNA genes. They cause plant diseases.
lysogenic cycle
integration and stabilizing of viral genes into the host cell’s genome
lytic cycle
host cell lyses, releasing many viral particles
induction
switch from lysogenic prophage to a lytic cycle
cancer
may be cause by viruses through triggering the expression of cancer-causing genes present in the genome.
prophage
parasitic viral DNA that has been integrated in chromosomes of bacterial host.
influenza virus
3 major types of flu virus (A B C).
only A can occur in human, other mammals and birds.
flu subtype is determined by the kinds of proteins representing the H and N protein spikes making up the capsid of the virus.
different strains of the virus requires different vaccines
genetic high mutation rates is primarily responsible for the high diversity in strains
genetic recombination between flu strains from different species is common
prion
misshapen protein agents with no associated nucleic acid that may convert other proteins in the cell to also become these agents causes Mad cow disease and others.
