Virology & Prokaryotes

Taxonomy

the science of naming and classifying organisms

Phylogeny

the evolutionary history of a group of organisms 

Phylogenetic tree

represents evolutionary relationships (not phenotypic similarity)

Taxon

groups organisms together based on shared characteristics

Evolution

changes in allele frequencies in populations over generations

Natural selection

beneficial traits increase over time, while less beneficial traits decrease

Viruses

subcellular, intracellular, parasites

Capsid

protective coat made of proteins (capsid proteins)

Capsid function

determines the morphology (shape) of the virus

Capsid proteins

determines the attachment to the host cell

Genome

made of DNA or RNA

Genome characteristics

single or double stranded

linear, circular, or segmented

Envelope

phospholipid bilayer surrounding the capsid

Characteristics of viruses

smaller than cells

replicate within cells

use the cell's resources for its own life cycle

Things viruses do not do/have

carry out metabolic processes 

reproduce independently of host cells 

contain any cellular structures (nuclei, cytoplasm, ribosomes, organelles) 

Viral replication steps

1. The virus binds to the host cell 

2. The genome enters the cell 

3. The genome replicates, and the viral genes are expressed 

4. The virus assembles 

5. The virus exists (bursts the host cell open)

Bacteriophages

viruses that infect bacteria 

Lytic cycle

virus replication cycle that kills the cell

Horizontal transmission

host-to-host transmission

Virulent phages

phages that carry out the lytic cycle 

Lysogenic cycle

 virus replication cycle that does not kill the cell

Vertical transmission

parent to offspring transmission 

Temperate phages

phages that carry out the lysogenic cycle