MBIO 3410 lecture Oct 18 2007

MBIO 3410 lecture Oct 18 2007 - Last Lecture overview...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Last Lecture - overview Aspects of protein synthesis Codon-anticodon interaction Wobble Ribosome binding site (RBS) Polysomes Initiator tRNA Mechanisms of protein synthesis Initiation in prokaryotes Elongation Aminoacyl-tRNA delivery Peptide bond formation Translocation Termination Initiation in eukaryotes Scanning Initiation Elongation Termination
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Bacteriophage vectors
Background image of page 2
3 Bacteriophage λ Virus that infects E. coli λ phage infection occurs as a result of the adsorption of the λ phage particle to the bacterial cell by binding to the maltose receptor The phage particle injects its linear DNA into the cell where it is ligated into a circle The DNA may integrate into the host genome by self-specific recombination, where it may remain dormant for a long time = lysogenic phase or It may replicate to form many phage particles which are released from the cell by lysis and cell death = lytic phase
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 Bacteriophage λ genome 48.5 kb genome The ends are the cos (cohesive) sites which consist of 12 bp single-stranded cohesive ends The cos sites are asymmetric but are equivalent to large (16 bp) restriction sites These sequences are complementary and can anneal with each other enabling the DNA to be circularized in the cell
Background image of page 4
5
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
6 λ genome Genes on the left-hand side of the conventional genome map code for head and tail proteins of the phage particle These are followed by genes whose protein products are concerned with recombination and lysogeny in which the circularized phage chromosome is inserted into the host chromosome and is stably replicated as a prophage To the right of the map are genes concerned with transcriptional regulation and prophage immunity to superinfection ( N , cro, cI ), followed by the genes for DNA synthesis, late function regulation ( Q) and host cell lysis The central region of the genome is dispensable for lytic infection and may be replaced by unrelated DNA sequence
Background image of page 6
7 Lysogenic pathway The phage DNA becomes integrated into the bacterial genome ( via homologous recombination between attP and the bacterial genomic attB site) and is replicated along with the bacterial DNA The prophage DNA remains integrated until it is induced to enter the lytic pathway Fig 1.21
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
8 Lysogeny The cII protein determines if lysis or lysogeny occurs: cII is required for the transcription of the cI repressor and for some of the genes required for phage DNA integration Active cII results in the lysogenic pathway Inactive cII results in the lytic pathway The cII protein is relatively unstable and is susceptible to cleavage and destruction by bacterial proteases When grown in rich medium the proteases are generally active, such that cII is degraded and λ lysis occurs Under conditions of E. coli starvation, the proteases are less functional and consequently λ will more frequently lysogenize
Background image of page 8
9 Lytic pathway Early transcription:
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 28

MBIO 3410 lecture Oct 18 2007 - Last Lecture overview...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online