Transposons and it's various applications

1. By-
Akancha Sinha
M17LS01

2. •TRANSPOSONS
• “Transposable elements”
• “Jumping genes”
• Mobile DNA
• – able to move from one place to another within
a cell’s genome
• – sometimes copy is made and the copy moves
• – insertion requires target DNA sequences.

3. Definitions and Keywords
•Transposase -An enzyme that binds to ends of
transposon and catalyses the movement of the
transposon to another part of the genome by a cut and
paste mechanism or a replicative transposition
mechanism.
•IS elements -A short DNA sequence that acts as a
simple transposable element

4. • These mobile segments of DNA are sometimes called
"jumping genes“.
• There are two distinct types of transposons:
1) DNA transposons
• -transposons consisting only of DNA that moves directly
from place to place.
2) Retrotransposons
• - first transcribe the DNA into RNA and then use reverse
transcriptase to make a DNA copy of the RNA to insert in a
new location.

5. BACTERIAL TRANSPOSONS
● In bacteria, transposons can jump from
chromosomal DNA to plasmid DNA and back.
● Transposons in bacteria usually carry an additional
gene for function other than
transposition---often for antibiotic resistance.
● Bacterial transposons of this type belong to theTn
family.
When the transposable elements
lack additional genes, they are known as
insertion sequences.

6. Bacterial Transposons
•
Bacteria contain two types of
transposons:
•
1]Composite mobile genetic elements that
are larger than IS elements and contain one
or more protein-coding genes in addition to
those required for transposition.
•
2]Non composite mobile genetic elements
are those which lack IS elements on its
ends e.g. is Tn3

7. Composite Transposon
A composite transposon, is flanked by two separateA composite transposon, is flanked by two separate
IS elements which may or may not be exact replicas.IS elements which may or may not be exact replicas.
Instead of each IS element moving separately, theInstead of each IS element moving separately, the
entire length of DNA spanning from one IS elemententire length of DNA spanning from one IS element
to the other is transposed as one complete unitto the other is transposed as one complete unit..
IR IR

8. Non composite Transposon
• Non-composite transposons (which lack flanking insertionNon-composite transposons (which lack flanking insertion
sequences). In each case, transposition requires specific DNAsequences). In each case, transposition requires specific DNA
sequences located at the ends (IS1, IS3, Tn5, Tn10, and Tn3) orsequences located at the ends (IS1, IS3, Tn5, Tn10, and Tn3) or
a multisubunit complex (e.g. Tn7).a multisubunit complex (e.g. Tn7).
• Encode transposition proteins, have inverted repeats (but noEncode transposition proteins, have inverted repeats (but no
ISs) at their ends. In addition to resistance and virulence genesISs) at their ends. In addition to resistance and virulence genes
they may encode catabolic enzymes.they may encode catabolic enzymes.

9. Mechanism of Transposons
There are two distinct types of
Transposons
•Replicative transposition – direct interaction
between the donor transposon and the target
site, resulting in copying of the donor element
•Conservative transposition – involving
excision of the element and reintegration at a
new site.

10. •1. Replicative
transposition

11. Replicative Transposition
Single stranded cuts are made on
either side of the Transposon and
on the opposite sides of the
target of the recipient.

12. • get This produces 4 free ends
in each DNA molecule
Two of the ends from the donor are
ligated to 2 of the ends of target.
This links the two molecules with a
single molecule of transposon.

13. The two remaining free 3’ ends are
used as primers for DNA polymerase
which uses the Transposon DNA
as the template.This replicates the
transposon and leaves the cointegrate.

14. • 2. Non-replicative
(conservative)transposition
• - Cannot copy transposon sequence
• - Transposition by cut and paste model
• Cut transposon sequence from donor
molecule attach to target site
• Ex. IS10, Tn10

15. NON REPLICATIVE
Transposonsition
First, the transposase makes a double-stranded cut in theFirst, the transposase makes a double-stranded cut in the
donor DNA at the ends of the transposondonor DNA at the ends of the transposon
and makes a staggered cutand makes a staggered cut
in the recipient DNAin the recipient DNA..

17. • Illustrate the mechanism of
transposition in transposons.

18. • Evolution of Transposons
• • Transposons are found in all major
• branches of life.
• • It arisen once and then spread to other
• kingdoms by horizontal gene transfer.
• • Duplications and DNA rearrangements
• contributed greatly to the evolution of new
• genes.

19. • Transposons causing diseases
• Transposons are mutagens. They can damage the genome of
their host cell in different ways:
• 1. A transposon or a retroposon that inserts itself into a
functional gene will most likely disable that gene.
• 2.After a transposon leaves a gene, the resulting gap will
probably not be repaired correctly.
• 3.Multiple copies of the same sequence, such as Alu
sequences can hinder precise chromosomal pairing during
mitosis and meiosis, resulting in unequal crossovers, one of
the main reasons for chromosome duplication.

21. • Applications
• • The first transposon was discovered in the plant
maize(Zea mays, corn species), and is named
dissociator (Ds).
• • Likewise, the first transposon to be molecularly
isolated was from a plant (Snapdragon).
• • Transposons have been an especially useful tool in
plant molecular biology.
• • Researchers use transposons as a means of
mutagenesis.

22. • To identifying the mutant allele.
• • To study the chemical mutagenesis
methods.
• • To study gene expression.
• • Transposons are also a widely used tool for
mutagenesis of most experimentally
tractable organisms.

23. Links for further reading1
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Molecular Cell BiolOGYMolecular Cell BiolOGY
BaltimoreBaltimore
-molecUlar biology of the gene Watson-molecUlar biology of the gene Watson
-Genes Lewin-Genes Lewin
-VOET AND VOET-VOET AND VOET
-LEHNINGER-LEHNINGER
-COOPER-COOPER