MBB 267 Week 4: Barnes 3 Flashcards
What is a transposon?
a DNA sequence that can change its position within the genome, sometimes creating or reversing mutations and altering the cell’s genome size”; aka “jumping gene
What are the 2 types of transposons?
two main classes of transposons:
- “cut-and-paste”
- “copy-and- paste”
- -they can be autonomous or non-autonomous
What are cut and paste DNA transposons contain?
The direct repeats (Generated from host genome during transposition) and then the inverted repeats (Part of the transposon proper; = transposase recognition site) then the gene (transposase)
What is a direct repeat?
direct repeat: simply the same sequence repeated in two places
What is an inverted repeat?
inverted repeat: a sequence plus its reverse complement
What is a transposase?
Transposase is an enzyme that binds to the end of a transposon and catalyses its movement to another part of the genome by a cut and paste mechanism or a replicative transposition mechanism.
How do transposases work?
Steps:
1-Transposase is transcribed and translated by the host machinery (gene could be from this transposon or another one elsewhere in the genome).
2-Transposase binds to the inverted repeats at the end of the transposon sequence
3-The enzyme cuts the DNA to remove the transposon from its original genomic location…
4-And creates a break at the target site to allow the transposon to be inserted at its new location.
5-Gaps filled with host repair enzymes.
6-Direct repeats are genrateed at the insertion site.
Where do transposons insert?
Some transposons have a preference target site, some insert randomly
What are Ac/Ds transposons?
So
- Ac = “Activator” = Autonomous: has its own transposase gene
- Ds = “Dissociation” = Nonautonomous: needs to use transposase enzyme from Ac. Same inverted repeat sequences as Ac.
What are bacterial mobile elements?
Same as in eukaryotes
