Transposition

Question 1

Transposition Basics 101

Answer 1

Definition: transposable elements (genetic units) mediate SELF-transposition from one place in a genome to another OR from one genome to another-e.g. from the bacterial chromosome to a conjugal plasmid (WITHIN THE SAME CELL) -relies on the ability of transposable elements to synthesize their own specific recombination enzyme

Question 2

Transposition 1-Clinical Relevance

Answer 2

-major carrier of AB RESISTANT GENES -can find their way to phage and conjugal plasmids==>general transfer of genetic material from cellcell & speciesspecies -evolution of R plasmid

Question 3

Transposition 2-Transposable Elements 101 (FOUR major types)

Answer 3

i. **insertion sequence (IS) elements ii.**transposons (Tn) iii. transposable prophages iv. conjugal transposon

Question 4

Transposition 3-Insertion Sequence (IS) Elements 1/2

Answer 4

-DNA segments 1000bp -only carry genes for transposition-including its own site-specific RECOMBINASE (TRANSPOSASE) anddd 2 distinct nucleotide recognition sequences located at each terminus in inverted order (-Recombinase=enzyme that recombines DNA) -If an IS element transposes into a gene it insertion will interrupt that gene (defective, loss of function) causing an INSERTION MUTATION

Question 5

Transposition 4-Insertion Sequence (IS) Elements 2/2

Answer 5

-transposition occurs INFREQUENTLY. -Recombinase must recognize the terminal inverted repeats AND a target area into which the new copy of the IS element will be inserted -After transposition into the target area, the original copy remains at its original site (sometimes original is removed)

Question 6

Transposition 5-Transposon 1/4 Basics 101

Answer 6

definition: transposable elements that carry genes necessary for transposition and other functions

Question 7

Transposition 6-Transposon Structure and Function 2/4

Answer 7

-MUCH larger than IS because they are hybrids. -hybrid consists of: a central core of genes bounded by two IS elements (IS elements carry genes for TRANSPOSITION) -core genes can encode for a variety of functions including resistance to antimicrobial agents (AB) and heavy metals

Question 8

Transposition 7-Transposon types 3/4

Answer 8

What GENES (type of transposons) you talkin bout, WIllis?!

a. AB resistance=transposon
b. genes for conjugation=conjugal transposons

(found in diverse organisms: streptococcus and bacteroides)

• conjugation aka means of transfer
• MULTIPLY resistant transposons jump from locationlocation within a given cell AND can mediate THEIR OWN transfer to other cells!!!!
  c. bacteriophage=transposable bacteriophages/PROphages
• phage genese permit lysogenic infection of a bacterial host
• can alternate between lytic growth and lysogeny
• during lysogeny can integrate ANYWHERE in a chromosome
• once integrated, can transpose itself to another location (i.e jump from phage genome to chromosome or plasmid)
• Found in Gram +/- bacteria -cross species, genus AND some!!!

Question 9

Transposition 7-Transposon 4/4

Answer 9

What is gene exchange?

Can move tranposons between cells=permits transfer of resistance from cell-to-cell intra AND inter-species