Biological Mutagens Flashcards
What is a Transposon?
A DNA sequence that can move from one genetic element to another, which contains genes additional to those required for transposition.
Where do Transposons insert?
Into (almost) random locations.
In what organisms are Transposons found?
Archaea, Bacteria, Eukarya.
In what organism were Transposons first discovered?
Maize (Corn)
What genetic elements do Transposons typically use to transpose?
Terminal insertion sequences.
What is the maximum length of a Transposon insertion sequence?
2kb
What is Phage Mu?
A bacteriophage in a Transposon. (Geneception)
Can Transposons replicate independently?
No - they must integrate into a target site and become part of the target replicon.
What elements do composite transposons feature?
One or a few genes between IS elements.
What elements do non-composite transposons feature?
Inverted terminal repeats and NO IS elements.
What is a conjugative transposon?
A larger transposon that contains tra genes.
What do the tra genes in a conjugative transposon allow?
Excision, circularisation, and conjugative transfer to a a homologous or heterologous host.
What major problem are conjugative transposons responsible for?
Antibiotic resistance
What are polar effects (with regards to transposons)?
Interruptions in coding sequences/transcriptional units downstream of a transposon insertion.
IS2 elements contain promoters reading outwards. What effects does this have on downstream genes?
They are turned on.
How do ts plasmids allow for selection of transposon insertion mutants?
The ts plasmid is allowed to integrate into the genome at 30°C. The T is then switched to 42°C and the plasmid is lost.
The cells can be selected by plating with the appropriate antibiotic.
Which important bacteria are genetically intractable for transposons?
Mycobacterium tuberculosis
Yersinia psestis
Treponema padllidum
What is an antibiotic resistance cassette?
A genetic element containing flanking sequences homologous to flanking sequences on a gene of interest, with an antibiotic resistance gene in the middle.
