CH 23/24 Viruses Flashcards
homology
similar trait in 2 or more species
What is Phylogeny
evolutionary history of a group of organism
- relationships based on shared characteristics
homoplasy
similar traits that are not homologous
convergent evolution
similar structures acquired independently
what are the characteristics of life
- composed of cells
- homeostasis
- response to stimuli
- growth/development
- reproduction
what is homeostasis?
use of energy to maintain a steady state
Virus characteristics
- sub-cellular (not alive)
- most do not have a cell membrane
- have DNA or RNA surrounded by a capsid (protein coat)
- classified by type of nucleic acid ^ or by type of host
Name and describe the 3 viral reproductive cycles
1) Lytic - destroys the host cell
2) Temperate viruses - do not always destroy their host’s cell
3) Lysogenic - virus replicates with DNA of living host
Lytic Cycle example 5 stages
phages (viruses that infect bacteria)
- attach to bacteria
- penetrate
- DNA and protein synthesis
- Assembly
- Release by Lysis (disintegration of cell wall or membrane)
Lysogenic Cycle 4 stages
- Attachment
- Penetration: phage DNA enters bacterial cell
- **Integration: Phage DNA integrates into bacterial DNA
- Replication: integrated prophage replicates when bact. DNA replicates
Endocytosis
the host cell envelopes the virus, and the virus is surrounded by an extra membrane from the host-cell membrane. it is then released into the host-cell cytoplasm
Human Viral Diseases: 3 types with examples of how they damage
1) Pathogenic viruses damage by: altering cell membrane, interfering with reproduction, massive virus accumulations, lysis
2) DNA Viruses cause: smallpox, herpes, respiratory infections, gastrointestinal disorders
3) RNA cause: the flu, upper respiratory infections, AIDS, some cancers
Plant Viruses: 4 general characteristics/way of spreading
- mostly RNA Viruses
- spread among plants by insects
- spread through plant via plasmodesmata
- generally reduce plant productivity but sometime harmless
Retroviruses: how do they work(3 stages) and what’s an example?
- use transcriptase (enzyme that makes DNA from RNA)
- Transcribe RNA genome into DNA intermediate (high mutation rate than DNA replication)
- Host uses DNA intermedia to synthesize copies of viral RNA
EX: HIV (causes AIDS)
Viroid: what is it, what does it cause disease in?
short strands of RNA with NO Protein Coat
- so small they are hard to destroy
- cause disease in plants
