announcements

Announcements

• Ch. 8 Part 2 Homework due today• Ch. 8 Part 3 Homework due Friday• Online quiz due at midnight TONIGHT• Lab tomorrow at 8 AM• Review Session: Tuesday March 4th at 9 AM

and 10 AM…Bring muddiest points

Bacterial GeneticsChapter 8 Part 3

Recap (2 Minutes)

What are the mechanisms by which bacteria can acquire new genes?

Answer:DNA-mediated transformation

TransductionConjugation

Revisiting Plasmids• Common to bacteria• Double stranded DNA• They have ori• Do not code information

critical to a cell’s life• Do provide an advantage

for certain environments• Vary in amount of genes

they carry: few to many• Narrow host range• Transferred by

conjugation• Resistance plasmid-

encode resistance to many antibiotics

Horizontal Gene Transfer: Chromosome Transfer

• Less common than plasmid transfer• Involves Hfr cells: High frequency

recombination• The plasmid integrates into the chromosome• So, part of the chromosome ends up getting

transferred to the F- cell

Horizontal Gene Transfer: Chromosome Transfer-Formation of Hfr Cell

Chromosome Transfer

Revisiting Transposons

• They can disrupt genes• They can also transfer genes from one

bacteria to another• 2 types: insertion sequence and composite

sequence

IS vs. Composite Transposons

The Role of Transposons In Antibiotic Resistance