ch 26
viral taxonomy as of 2018→naming and classifying viruses. there are 2000 virus species.
calssified on the basis of nucleic acid type, envelope, capsid shape, size.
o why is phylogenetic history difficult for viruses?→because of horizontal gene
transfer between unrelated viruses and also the host. ; comparisions of folds of the
proteins and genome sequences in capsid proteins. however retrovirus and reverse
transcribing DNA viruses share common evolutionary history.
o what common ammong viruses ?→they all use reverse transcriptase
Baltimore system; plus and minus strands→used to identify the viral genome and the
method used to form viral mRNA; ssRNA with RNA genome identical to the mRNA is
positive strand RNA genomes and other are minus or negative strand.
dsDNA replication process→similar to cellular orgasnimsm to relies on the host RNA
and DNA polymerase for replication
Bacteriophage T4 lytic infection process→T4 attachment begins with a long tail fiber
contacts the lipopolysaccharide or certain protein in the outer membrane of e coli host, as
more tail fibers make contact the baseplate settles down and changes shape and tail sheat
shortens and becomes wider a central tube is inserted into the cell wall and linear DNA is
extruded.
o Wht happens after the linear DNA from the T4 phage is extruded into E coli?
→within 2 min Ecoli RNA polymerase starts making "early" T4 mRNA. earliest
T4 genes expressed encodes for a protein that binds to RNaseE which degrades
host mRNA thus freeing nucleotides and ribosomes for viral transcription and
translations. After 5 min, late mRNA is synthesized when viral DNA uses virus
encoded DNA dependent DNA polymerase.
viral taxonomy as of 2018→naming and classifying viruses. there are 2000 virus species.
calssified on the basis of nucleic acid type, envelope, capsid shape, size.
o why is phylogenetic history difficult for viruses?→because of horizontal gene
transfer between unrelated viruses and also the host. ; comparisions of folds of the
proteins and genome sequences in capsid proteins. however retrovirus and reverse
transcribing DNA viruses share common evolutionary history.
o what common ammong viruses ?→they all use reverse transcriptase
Baltimore system; plus and minus strands→used to identify the viral genome and the
method used to form viral mRNA; ssRNA with RNA genome identical to the mRNA is
positive strand RNA genomes and other are minus or negative strand.
dsDNA replication process→similar to cellular orgasnimsm to relies on the host RNA
and DNA polymerase for replication
Bacteriophage T4 lytic infection process→T4 attachment begins with a long tail fiber
contacts the lipopolysaccharide or certain protein in the outer membrane of e coli host, as
more tail fibers make contact the baseplate settles down and changes shape and tail sheat
shortens and becomes wider a central tube is inserted into the cell wall and linear DNA is
extruded.
o Wht happens after the linear DNA from the T4 phage is extruded into E coli?
→within 2 min Ecoli RNA polymerase starts making "early" T4 mRNA. earliest
T4 genes expressed encodes for a protein that binds to RNaseE which degrades
host mRNA thus freeing nucleotides and ribosomes for viral transcription and
translations. After 5 min, late mRNA is synthesized when viral DNA uses virus
encoded DNA dependent DNA polymerase.
