plasmids

• small, extra-chromosomal DNA elements
• not part of the chromosomes, much smaller than the chromosome
• must have an origin of replication

homologous recombination

• two DNA sequences that are similar (not identical) can exchange genetic material between the sequences
• this results in genetic change and ultimately variation 
• major protein required = RecA

RecA

• required for homologous recombination
• binds ssDNA
• aligns similar sequences with one another to set up for homologous recombination 

Natural transformation

• competent cells - express genes needed to undergo transformation 
• requires energy
• genetically encoded whether the microorganism can undergo transformation or not
• cells bind only dsDNA
• only ssDNA can enter 
• one strand gets degraded, while the other is maintained

synthetic (artifical) transformation

• not genetically encoded for
• does not require energy from the bacteria
• competent cells are present, but were MADE to competent

Griffith

• discovered transformation by working with R and S strains (with or without the capsule)
• somehow, the cells that lacked the capsule were able to uptake genes that encode for the capsule

transduction

• DNA packaged inside a bacteriophage partical enters a host cell
• is INsensitive to DNase
• requires the phage to be present 
• sometimes mistakes are make and donor DNA gets packaged into the bacteriophage

two types of transduction

• generalized - can move any part of the donor genome
• specialized - can only move a specific portion of the donor genome, these are adjacent to the phage insertion site

conjugation

• transfer of DNA during cell-to-cell contact
• INsensitive to DNase 
• Tra genes - are used for the production of teh sex pilus, which connects the two cells together, and how the DNA transfer occurs 
• F plasmid can be used

F plasmid

• donor has F+, recipient doesnt (F-)
• F plasmid gets transferred into the recipient, where it becomes F+
• the recipient cell is nor ready to be a donor cell 
• OriV - origin of replication thats used all the time
• OriT - origin of transfer/replication 
• DNA is replicated in both cells 

Hfr Strain

• high frequency recombination strain
• if the F plasmid inserts itself into a chromosome, then the chromosome becomes Hfr, but still is F+
• transfer begins at OriT, recipient will have a little bit of F+, but not all of it, and some chromosomal DNA
• the recipient is no longer F+, stays F- even if a little bit is present
• needs Hfr to move chromosomal DNA
• takes 100 minutes