DNA transposition Flashcards
1
Q
what are transposons?
A
- mobile genetic elements i.e. DNA sequences that carry genes enabling their movement within or between genomes.
Plasmids, viruses and cassettes or integrones are also MGEs
2
Q
where are transposons found?
A
in all genomes; bacteria to man.
- can carry antibiotic resistance genes
- cause genome instability and affect gene expression, contribute to genome evolution
3
Q
what is in the structure of a typical bacterial transposon; Tn3
A
- target site duplication at each end
- transposase
- binding site; where resolvase protein represses transcription of transposase gene and its own gene and where it catalyses resolution by recombination across two copies of Tn3 in a cointegrate
- B-actamase
- left and right inverted repeats (38bps)
4
Q
DNA transposons move by one of two mechanisms
A
- cut and paste; no increase in copy number
- replicative transposition; goes via cointegrate intermediate producing two copies from one
5
Q
transposons in eukaryotic cells
A
applied as genetic tools for mutagenesis and gene isolation
6
Q
what are transposons used for?
A
- identify essential genes
-introduce transposons on plasmid into cells - allowit to jump into genome
- grow up cells
- establish location of transposons by PCR
- genes that are never disrupted are essential
7
Q
what did Ig genes and RAF recombinase come from?
A
a transposon
8
Q
what are retroelements?
A
- mobile genetic elements
- transpose via an RNA intermediate
- cope and paste mechanism
- require reverse transcriptase (RT) activity
- best known examples ; retroviruses like HIV
9
Q
what are defective retro-elements?
A
LINES and SINES comprise 30% of human genome.
One million copies of the Alu (SINE) sequence
10
Q
summary on lecture points
A
- genomes require constant repair
- multiple repair pathways
- link betwen replication, repair and recombin. (transcription)
- DNA, though carrying genetic code, isn’t static; contains movable genetic elements
- highly active scientific field
