MBG Part Two: Lecture 15 Flashcards
What are simple transposable elements?
Only carry information required for movement
What does simple transposable elements contain?
Insertion Sequence (IS) such as IS1 - common in EColi.
(800-2000bp in length)
- The transposase gene
- Contain terminal inverted repeats
- Contains Flanking Direct Repeats
What are complex transposable elements?
Contain extra DNA information not related to transposition
What do complex transposable elements contain?
Can contain Composite Transposons or Non-Composite Transposons
What is a composite tranpsoson?
Any sequence that is next to two simple transposable elements
What does a Flanking Sequence mean?
The nucleotide sequences that are next to a specific DNA sequence of interest.
What is Tn10 an example of?
A composite transposon
- 9300bp that carries the tetracycline resistance gene flanked by 2 IS10 insertion sequences
What are non-composite transposons?
Posesses the transposase gene and have terminal inverted repeats
What is Tn3 an example of?
A non-composite transposon
- Carries the ampicillin resistance gene
What did Barbara McClintock Study?
Chromosome Breakage
What did Barbara McClintock discover?
That during chromosome breakage the clear kernels became a mosaic with brown-purple patches
What did Genetic Analysis of the Mechanism of Chromosome Breakage lead her to?
To discover the cut and paste of Ds and Ac elements that moved around the genome
What was Mosaic Colouring in the corn caused by?
2 unstable “genes”
- Ac Activator Gene
-Ds-Dissociation Gene
What does the Ac Activator Gene Contain?
- Terminal Inverted Repeats
- The Transpsase Gene
- Autonomous Transposition (contains everything it needs)
What does the Ds Disscociation Gene Contain?
- The inactivated transposase gene
- Requires the transposase from Ac to transpose
- Non autonomous transposition (needs activator to start it)
What does Ac stimulate?
Chromosome breakage at the start of Ds
What genotype for corn would produce no transposition?
cc (yellow) and Cc (purple)
What transposition gene will produce a yellow kernel?
Going from Cc to Ctc (yellow)
What transposition gene will produce a mosaic kernel?
Going from Ctc to Cc/Ctc (mosaic)
What is a P element in Fruit Flies?
DNA transposons
What does this P element posses?
Terminal inverted repeats and both a transposase and a repressor of transposition
What do these P elements creat?
Hybrid Dysgenesis
What is Hybrid Dysgenesis?
When P elements are introduced into a cell that does not have them in its genome
What does Hybrid Dysgenesis create?
- A sudden burst of mutations
- Sterile Offspring
What is a repressor protein?
A cytoplasmic protein that inhibits transposition
What are Repressor Proteins incorporated into?
The cytoplasm of the egg P+ female
What happens if a P+ female is crossed with a P- male?
The inhibition of the repressor proteins will prevent transposition (blocking it) and the fly will be wiltype (fertile)
What happens if a P- female is crossed with a P+ male?
It will produce a sterile offspring as the males sperm does not have a sufficient amount of repressor proteins to inhibit transposition
What is the most common transposable element in the human genome?
Alu.
What is Alu an example of?
SINES
What is SINES?
Non autonomous transposable elements in Eukaryotes
- Identified as mutagenic in more then 20 genetic diseases
What did SINES arise from?
RNA intermediate (shortened 5’ end)
What do SINEs contain?
Short flanking repeats when sequences inserted into DNA
What are LINES?
Have shortened sequences but longer than SINES
