Horizontal Gene Transfer Flashcards
Ways foreign DNA enters the cell
Transformation
Transduction
Conjugation
Once inside the cell, DNA can
Be degraded/lost
Replicate as separate entities (plasmids, phage)
Be integrated into the chromosome
How is DNA integrated into the chromosome
Recombination
Transposition
Important type of genetic recombination
Homologous recombination
HR important for
DNA repair (double strand breaks)
Key player in HR
RecA
What does RecA do
Binds single stranded DNA, searches for homologous DS DNA, mediates strand invasion
Mobile genetic elements found in almost all species
Transposable elements
Transposable elements contain
Transposase gene, inverted repeats
What do transposase enzymes do
Recognize inverted repeats, cleaves DNA to free the transposable element, cleaves different DNA and inserts TE into it
Two kinds of transposable elements
Conservative (cut and paste)
Replicative (copy and paste)
What is transformation
Free DNA incorporated into recipient cell by competent bacteria
How does transformation work
DNA from environment captured by pili, retract, bring DNA through OM/CW
One strand is degraded, other passes through CM into cell
Virus that infects a bacterium
Bacteriophage
Virus DNA packed into
Virions
Temperate bacteria can
Operate through the lytic or lysogenic pathway
What is lytic vs lysogenic
Lytic = virus DNA replicates in host cell using resources then lyses cell
Lysogenic = DNA integrated into host DNA (prophage)
What is transduction
Virus transfers DNA from one cell to another
Two types of transduction
Generalized: host cell DNA accidentally packaged into viral particle during lytic cycle
Specialized: prophage DNA excised and packaged, neighbouring DNA accidentally packaged
Secretion system in conjugation
Type four
What is an Hfr cell
Insertion sequence of F plasmid can be integrated into chromosome producing Hfr cell
Donors chromosomal DNA may also be transferred and incorporated
