Taxonomy Flashcards
Viruses
(virion)- consists of nucleic acid core surrounded by a protein coat called a capsid. smaller than bacteria. Not living- classified separately, based on common characteristics:
Capsid make up
proteins called capsomeres- determines shape of virus.
bacteriophage
virus that affects bacteria;
cell makeup of viruses
acellular and cannot independently perform metabolic activities
virus reproduction
Can reproduce but only within other cells- takes over the cell’s genetic information
Virus nucleic acid
Nucleic acid=DNA or RNA but not both. DNA–single or double stranded.
virus classification
type of nucleic acid (DNA/RNA…see recording). presence/absence of capsid
virus origin
Virus came from bits of nucleic acids that “escaped” from cellular organisms (transposons or plasmids) in plants, animals, or bacteria
plant virus can only infect plant
Lytic cycle-
type of virus reproductive cycle. lyses or destroys host cell. Viruses that only have lytic cycles are virulent
Attachment or absorption
viruses attach to receptors on host cell wall or cell membrane
Penetration-
nucleic acid moves from virus into cytoplasm of host cell
Replication and synthesis
virus degrades host cell nucleic acid and uses host cell to synthesize necessary components for its replication
Assembly
newly synthesized viral components are assembled into new viruses
Release
new viruses are released from cell. Lytic enzymes produced by phage destroys host’s plasma membrane
Steps of lytic cycle
Attachment or absorption, penetration, Replication and synthesis, Assembly, Release
Temperate viruses
do not always destroy their hosts. They have lysogenic cycle in which the virus become integrated into the hosts
Temperate viruses details
This virus replicates when the host cell replicates. Certain external conditions can cause them to revert to a lytic cycle, or they may remain repressed indefinitely.
Viruses that infect animal cells
May have DNA–DNA from virus integrates into DNA of the host cell
May have RNA–in some, used as mRNA in the host cell
retroviruses
infect animal cells; Reverse transcriptase produces DNA from the RNA, which then becomes integrated into the host DNA, which is used to make RNA again (HIV is ex)
Viruses that infect plant cells
Because plants have thick cell walls, viruses cannot penetrate plant cells unless they are damaged. Once enters- spreads through plant via plasmodemata. Most RNA viruses
Symptoms: reduced plant size, spots or streaks on leaves, flowers or fruits
Viroid-
smaller than a virus, has no protective protein coat, Consists of short strand of RNA; Cause plant disease
Prion
“proteinaceous infectious particle”- animals have a gene that codes for this prion (208 amino acids)- normally harmless. But it can convert to a different shape and cause disease
tobacco mosaic virus
infects tobacco plants
Bovine spongiform encephalopathy-
“mad cow disease”- prion. cattle became infected when ate feed containing infected brains and organs from sheep
