2.7 Transposable elements Flashcards
What are transposable elements?
Sequences that can move about the genome
What is transposition?
Movement of the transposons
What are some features of transposable elements?
flanking direct repeats, terminal inverted repeats
What do Transposable elements usually cause?
mutations
What does not travel with the transposable element?
Short flanking repeats
Where are the short flanking repeats regenerated?
at the point of insertion
Staggered cuts are made in where, that leave what on the transposable element?
Are made in the target DNA, leaving short, ss pieces of DNA on either side of the transposable element
What are three things about the inverted repeats?
They are inverted/complimetary on same strand. Recognized by enzymes that catalyze transposition. Required for transposition to take place.
True or False? Transposons have their own info to replicate and cut themselves out.
True
What two ways do transposons cause mutations?
Inserting into another gene, promoting DNA rearrangements.
What is an example of mutation caused by transposons?
Grape color
What are 3 common features in mechanisms of transposition?
Staggered breaks made in target DNA, transposable element is joined to ss ends of the target DNA, DNA is replicated at the ss gaps.
What is replicative transposition referred to as?
Copy and paste
What is replicative transposition?
New copy of transposable element is introduced at a new site while the old copy remains in the original site.
What results from replicative transposition?
Increase in the # of copies of the transposable element.
Where can replicative transposition occur?
Between two dif DNA molecules or between two parts of the same DNA molecule
What events are necessary for co-integrate formation of replicative transposition?
Singly copy of the TE is on one DNA molecule, two DNA molecules are joined, TE is replicated, resulting in the production of a cointegrate structure.
What is the cointegrate structure?
Two DNA molecules plus 2 copies of the TE
What is the resolution of the cointegrate?
Crossing over at regions within the copies of the TE produces 3 molecules, each with a single copy of the TE.
What enzymes are needed for replicative transposition?
Transposase and Resolvase
What is Transposase?
Allows movement
What is Resolvase?
Allows integration to occur
What is non-replicative transposition referred to as?
Cut and paste
What is non-replicative transposition?
TE is excised from old site and inserted into a new site. DOESNT increase number of copies
What are euk transposons?
SINEs and LINes
What are retrotransposons?
Transpose through an RNA intermediate. Only done through replicative transposition. More commonan than DNA transposons in euk
What are the theories of TE and genomic elvolution?
Parasites, providing no benefit but harm. OR. Exist to increase genetic diversity, parasitic tendencies replaced to be useful to cell.
What is a consequence of transposed sequences?
Chromosomal rearrangements
Who is barbara McClintock?
Discovered TE and used it to demonstrate genes are responsible for turning physical characteristics on and off. Kernels in corn color are from jumping genes
What can also be influenced by transposons?
Tomato shape
How can transposons change tomato shape?
Caused a translocation
What was the 1st report of transposons moving in humans?
L1 element which resulted of retrotransposition into the Factor VIII gene, causing de novo hemophilia.
What have transposons helped in pertaining to evolution of mammals?
Evolution of pregnancy in mammals.
What type of disease can retrotransposons cause in humans?
single-gene disease
How is p53 linked with transposons?
P53 has lots of roles. Like educing apoptosis. It’s a tumor suppressor, its inactivated in half of the cancers. It suppresses transposon activity.
