Final Exam: Exam 5 pt 3 Flashcards
Genetic recombination
-physical exchange of genes between genetic elements
main enzyme in genetic recomination
Rec A, also helps in SOS response
homologous recombination
-exchange of very two similar pieces of DNA between different sources
Eukaryotes homologous recombination
-vertical gene transfer
-occurs during meiosis
Prokaryotic homologous recombination
-horizontal gene transfer
-more common than previously thought
-occurs by three different mechanisms
transformation
-involves the uptake of naked DNA from the environment
-pick up random DNA laying out
Transformation experiment
-1920 Frederick and Griffith
-streptococcus pneumoniae
-R strain: nonvirulent
-S strain: virulent
-other bacterial cells can take up broken down capsule DNA and become virulent
Mechanism of transformation (basic)
-look for DNA binding proteins to be expressed by bacterial cell (integral)
-DNA uptake around 10 Kb
Mechanism of transformation (detail)
-DNA binding complex resemble type IV fimbriae
-bind double stranded DNA and then shorted and converted to single strand fragments
-once in cell, bound to single stranded DNA binding proteins
competent
-bacteria that can take up DNA from the environment and be transformed
-do this when environment is stable
factors that determine competency
-genetically
-regulated: happens at certain times (induced when environment is favorable)
-variation is seen regarding when and how many are competant
naturally competent bacteria
-bacillus
-streptococcus
-haemophilus
-neisseria
-acintobacter
high efficiency natural transformation
-rare
-force bacteria to become competency (E coli)
electrical shock (electroporation)
-force competency
-chemical signal that stunts cell membrane and let DNA in
exposure to calcium chloride
-force competency
-then chilled to take up DNA
Transduction
-DNA transfer mediated by a bacteriophage
bacteriophage
viruses that inflict bacteria
lytic virus
get in, multiply, lyse (release)
lysogenic viruses
-hanging out for awhile
-can go into lytic
generalized transduction
-happens in lytic phase (or when lysogenic becomes lytic)
-random fragments of disintegrating host DNA taken up by the phage during assembly
quality control
only check for size of fragments, not the correct genes
specialized transduction
-highly specific part of host genome is regularly incorporated into the virus
-only occurs with lysogenic phage
-insert themselves into chromosomesp
process of specialized transduction
–prophage in bacteria
-excised phage contains some bacterial DNA
-new viral particles synthesized
-infection recipient cell transfers bacterial DNA to new cell
when phage isnt infectious anymore, it can still
-exchange bacterial DNA w other bacterial cells
