Lecture 7 Flashcards
What is the function of viral genes?
encodes structural components and enzymes for the viral life cycle
What is needed for viral multiplication?
- viral genes
- enzyme function
- resources from host cell
- viral enzyme
What components are supplied by the host cell?
- ribosomes
- tRNA
- energy production
What do enzyme functions help with?
- penetrate host cell
- replicate viral nucleic acid
- initiating protein synthesis
What does a virus need in order to multiply?
- invade a host cell
- take over host’s metabolic machinery
What is the bacteria’s eclipse period?
bacteria is denaturing within the cell and can’t be seen
What is the lytic cycle?
phage causes lysis and death of host cell
What is the lysogenic cycle?
- phage DNA is incorporated into the host DNA
- phage conversion
- specialized transfuction
What are T-even bacteriophages?
T (even number) bacteriophages
- just for identification for different bacteriophages
What are the steps of lytic cycle?
1) attachment: phage attaches by tail fibers to host cell
2) penetration: phage lysozyme opens cell wall, tail sheath contracts to force tail core and DNA into the cell
3) biosynthesis: production of phage DNA and proteins
4) maturation: assembly of phage particles
5) release: phage lysozyme breaks the cell wall
What are lysogenic phages?
- temperate phages
- incorporate their DNA into host cell DNA to begin lysogenic cycle
What is lysogeny?
phage is inactive
- bacterial host cells are known as lysogenic cells
What are the important results of lysogeny?
1) Lysogenic cells are immune to reinfection by the same phage
2) phage conversionn, host cell may exhibit new properties
3) makes specialized transduction
What is specialized transduction?
specific bacterial genes transferred to another bacterium via a phage
- changes genetic properties of the bacteria
What is attachment of viruses?
sticking to complementary receptor sites
- receptor cites are made of proteins and glycoproteins
- spike attaches to receptors
What is entry of a virus?
step that follows attachment
- receptor-medidated endocytosis
- plasma membrane fold inwards to form vesicles
- enveloped viruses enter through fusion
What is uncoating of a virus?
separation of viral nucleic acid from protein coat
- animal cells uncoat by lysosomal enzymes (degrading protein of viral capsid)
What are the steps of biosynthesis?
1) attachment
2) entry and uncoating
3) transcription
4) biosynthesis
5) translation
6) maturation
7) release
What is adenoviridae?
respiratory infection in humans
- double stranded DNA (not enveloped)
- conjuctival infection
- gastroenteritis
- tumors in animals
What is poxviridae?
- enveloped double-stranded DNA
- skin lesions
- complex version of chicken pox
What is herpesviridae?
- enveloped double stranded DNA
- spiked
What is papovaviridae?
- nonenveloped double-stranded DNA
- warts
- can transform cells and cause cancer
What is hepadnaviridae?
- enveloped double-stranded DNA
- Hepatitis B virus
- uses reverse transcriptase to make DNA into RNA
