1. TRANSPOSABLE ELEMENTS
&
TRANSPOSABLE ELEMENTS IN
BACTERIA:
Insertion sequences (IS).
SEMINAR REPRESENTED BY
QAMRUNNISA ABDUL WAHID SHAIKH
MSC-II (MICROBIOLOGY)
MB702-Molecular biology
3. These are discrete sequences in the genome that are
mobile-they are able to transport themselves to other
locations within the genome.
Transposable elements make up a large fraction of the
genome and are responsible for much of the mass of DNA in
a eukaryotic cells.
TRANSPOSABLE ELEMENTS(TE)/JUMPING
GENES/MOBILE ELEMNETS:
These sequences are found in all organisms.
45% of human genome.
90% of maize genome
5. These elements encode enzymes that can
insert their sequence into new sites.
Terminal inverted repeats
are generally present
at the ends.
They generate direct repeats at the point of
insertion.
GENERAL CHARACTERISTICS:
8. 8
Transpose through RNA intermediate, are transcribed from
transposable element and are then copied back by reverse
transcriptase.
Retrotransposons are more common in eukaryotes.
RETROTRANSPOSONS(CLASS I):
DNA TRANSPOSONS (CLASS II):
These transpose to new sites directly as DNA.
These are more common in prokaryotes.
9.
10. The process by which these sequences are copied and
inserted is called as transposition.
On the basis of mechanism involved.
TRANSPOSITION:
11. AUTONOMOUS AND NONAUTONOMOUS
TRANSPOSONS:
Autonomous transposable elements : Autonomous TEs can move
on their own. For example Ac elements
Non autonomous transposable elements : Require the presence of
other TEs in order to move.For example Ds elements
12. 1.Insertion sequences (IS).
2.Composite transposons.
3.Non composite transposons.
They generally use non-replicative transposition.
TRANSPOSABLE
ELEMENTS IN BACTERIA:
13. 1.INSERTION SEQUENCES (IS):
Simplest form of transposable elements found in prokaryotes.
First discovered in connection with genes controlling galactose
utillization in E.coli.
Prefix – IS followed by number. Examples: IS1,IS2,IS3 etc
700 IS elements
Normal constituent of bacterial chromosome and plasmid.
Autonomous unit
Short inverted repeats
Transposase
17. EFFECT :
Gene inactivation
Mutation
Gene alterations (Insertions, excisions, Duplication or
translocation)
Disease that are caused by TE:
Hemophilia A & B,
X-linked severe combined immunodeficiency,
Porphyria, cancer etc.
SO ARE TRANSPOSONS GOOD OR
18. USES :
Recent research has shown that transposons may help plants
respond and adapt to environmental stress by regulating other
genes.
In bacteria, transposons often carry genes that impart resistance
to antibiotic substances, helping the bacteria survive.
Insertional mutagenesis (induced mutation)
The Sleeping Beauty transposon system is a synthetic DNA
transposon designed to introduce precisely defined DNA
sequences into the chromosomes of vertebrate animals for
the purposes of introducing new traits and to discover new
genes and their functions
19. CONCLUSION:
Early view of mobile elements as junk DNA or completely
selfish molecular parasites appears to be premature.
Rather, they probably have made profound contributions to
the evolution of higher organisms by serving as the sites of
recombination, leading to the evolution of novel genes and
new controls on gene expressions.