Lecture 11: Viruses and Tree of Life Flashcards
what is life?
- organized
- able to replicate itself
virus structure
- protein coat (capsid)
- DNA or RNA
- no cytosol
- no plasma membrane
capsid/protein coat
-contains core that contains nucleotides
viral hereditary material
- DNA or RNA but never both
- circular or linear genetic material
- single or double stranded
- need a host cell in order to replicate
virions
-individual virus particles
helical shapes
- circular, spherical
- plant and flu viruses (influenza)
icosahedral shapes
- geometric solid
- maximizes internal capacity
binal
-have both icosahedral and helical shapes
basics of viral replication
- virus enters cell
- cell strips off virus outer coat of protein
- nucleic acid in virus released
- nucleic acid gets into cells chemical manufacturing system
- cell switches to making new viruses
- cell sometimes destroyed in the process
bacteriophage
- very small
- virus that infects bacteria
why do some scientists argue that viruses are not alive? why do others disagree?
- bc they need a host to replicate, they’re not traditional cells
- others bc they are highly organized, they have the same kind of genetic storage as living things, they figured out how to replicate, they mutate, and evolve (even evolved from LIVING things)
TSE
- aka transmissible spongiform encephalopathies
- virus that causes cavities in the brain
- can get it from being injected with infected tissues, transplant of infected tissues, or eating infected tissue
TSE examples
-types: scrapie, bovine spongiform encephalopathies (mad cow disease), chronic wasting disease, creutafeldt-jakob disease
prions
- prions don’t contain DNA (we know this b/c we hit them with radiation that would kill DNA but they’re fine)
- they’re misfolded protein
why were prions originally called slow viruses?
-the time between infection and detection is very long
prion “replication”
-misfolded prion protein touches normal protein and makes it misfolded
how is the traditional (5 or 6 kingdom) view of the tree of life biased?
- protists are actually paraphyletic and the traditional tree makes it look like all groups are equal in size
- archaea and bacteria are actually very different than the rest
three domain model
- Bacteria, Archaea, Eukarya
- better bc it shows complexity more
- might soon change to 2 domain model though
LUCA
- Last Universal Common Ancestor
- all life shares some traits, indicating existence of LUCA
traits shared by all life forms
- have plasma membrane bound cells and ribosomes
- semi-conservative DNA replication
- use DNA to encode proteins
- use same genetic codes to produce proteins
- do transcription/translation
- metabolize through similar pathways
key traits common to bacteria and archaea
- unicellular
- binary fission
- unenclosed DNA
- circular chromosomes
- no organelles
- asexual
defining traits of Eukaryotes
- multi-cellular
- compartmentalized
- sexual (mostly)
how is the new eukaryotic tree different from older views?
-includes protists (eukaryotes that aren’t plants, animals, or fungi)
