This document discusses transposable elements, which are discrete DNA sequences that can move to different locations within a genome. It covers the history of their discovery, mechanisms of transposition, classification into retrotransposons and DNA transposons, and examples found in bacteria. Specifically, it describes three types of bacterial transposable elements - insertion sequences, composite transposons, and non-composite transposons. The effects of transposable elements include gene inactivation, mutation, and their role in disease, but they can also help organisms adapt to stress and confer antibiotic resistance in bacteria.

1. TRANSPOSABLE ELEMENTS
&
TRANSPOSABLE ELEMENTS IN
BACTERIA:
Insertion sequences (IS).
SEMINAR REPRESENTED BY
QAMRUNNISA ABDUL WAHID SHAIKH
MSC-II (MICROBIOLOGY)
MB702-Molecular biology

2. CONTENT:
Introduction
History
General characteristic
General mechanism
Classification
1) Retrotransposons
2) DNA transposons
Transposition
1) Replicative
2) Non replicative
Bacterial transposons
1) IS elements
2) Composite transposons
3)Non composite transposons
Effects of transposons
Uses of transposons
Conclusion

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

4. 4
HISTORY:
Barbara McClintock discovered transposable
elements in 1948 in maize for which she was
awarded noble prize in 1983 for her discovery of
TEs.

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:

6. GENERAL MECHANISM:

7. CLASSIFAICATION OF
TRANSPOSABLE ELEMENTS:
Yeast : Ty elements
Drosophilla : Copia
elements
LINES
SINES
Bacteria : IS elements
Drosophilla:Pelement
s
Corn : AC/ DC
elements

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.

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

14. MAECHANISM OF TRANSPOSITION:

15. Transposons
Target
repeats
(bp)
Inverted
repeats
(bp)
Overall
length
(bp)
Target
selection
IS 1 9 23 768 Random
IS2 5 41 1327 Hotspot
IS3 11-13 18 1428 AAAN20TT
IS4 4 16 1195 Hotspot
IS10R 9 22 1329 NGCTNAGC
N
IS50R 9 9 1531 Hotspot
IS903 9 18 1057 Random
EXAMPLE:

16. 2.COMPOSITE TRANSPOSONS.
3.NON COMPOSITE TRANSPOSONS.

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.

20. REFRENCES:
GRIFFITHS_-_introduction_to_genetic_analysis
Lewin s Genes 11E (LSA Gwalior).pdf filename=UTF-8
Lewin 27s 20Genes 20(1)
Google

22. THANK YOU