MOBILE ELEMENTS BACTERIAL TRANSPOSONS HUMAN TRANSPOSONS DROSOPHILA TRANSPOSONS

1. TRANSPOSABLE
ELEMENTS
VARSHA YADAV
ROLL NO.- 6674
DEPARTMENT OF
BIOTECHNOLOGY
CENTRAL UNIVERSITY OF
HARYANA

2. INTRODUCTION:
Transposons are section of the genome that undergo
transposition with in the genome.
Discovered by Barbara McClintock in corn in 1940.
They are known as transposable elements, mobile sequence,
movable sequence, insertion elements, jumping elements or
selfish DNA.
Later in 1960 bacteria and bacteriophages were shown to
posses TE.

3. CLASSIFICATION ON THE BASIS OF
MECHANISM OF TRANSPOSITION

4. CLASS 1:
Insertional sequence were the first transposable
elements identified as spontaneous insertion in some
bacteria operon.
They encode for transposase and are short about
800 – 1500 base pair.
IS carry the genetic information necessary for their
transposition .
Cut and paste mechanism.
There are different IS such as IS1, IS2, IS3, IS4.

7. CLASS 2 :
- These are called retrotransposon.
- Use the enzyme reverse transcriptase and then
make a copy of DNA and then inserted into the
genome in new position.
- Behave like retrovirus such as HIV
- Copy and paste mechanism
- Inverted repeats are present on either side.

9. (A) COMPOSITE TRANSPOSONS
 Carry genes (ex. Gene for antibiotic resistance) flanked on both sides
by IS elements.
 Tn10 is 9.3 kb in size includes 6.5 kb of central DNA (includes a gene
for tetracycline resistance) and 1.4 kb inverted IS element.
 IS element supply transposase and ITR recognition signals.

10. (B)NONCOMPOSITE TRANSPOSONS
 Carry genes ( ex. Antibiotic
resistance) but do not terminate
with IS elements.
 Ends are not IS element
repeated sequence.
 Tn3 is kb with 38 bp ITRs and
includes 3 genes; β-lactamase,
tnpA (transposase) and tnpB
(resolvase).

11. EXAMPLES OF TRANSPOSABLE
ELEMENTS
Ac-Ds system in MAIZE
P Element in Drosophila
LINEs and SINEs in Human

12. Ac-Ds element
Ac stands for activator and Ds for dissociation element.
Both were located on chromosome 9.
Transposition of Ds element altered kernel coloration.
Movement of Ds element requires activity of Ac element
that codes transposases.
Ac element is 4563 bp long and its structure is similar to
that of bacterial transposons.

14. P Element
Most significant transposable element found in drosophila
Range from 0.5 to 2.9 kb long , with 31 bp ITRs.
They encode two protein ,one is transposase enzyme that
activate transposition and another is a repressor that
inhibit transposition.
If P elements inserts into the coding region , it can
terminate transcription ,in introns affect splicing.
If inserts into the promoter region, it affect the level of gene
expression.

15. LONG INTERSPREAD OR SHORT
INTERSPREAD ELEMENTS
LINEs accounts for 21% of human genome and about 6kb
pairs in length.
SINEs accounts for 13% of human genome and are about
100-500bp long.
Most human transposons appear to be inactive but several
mutation lead to their activation.
LINE inserted into the human dystrophin gene have result in
Duchene muscular dystrophy.
LINE inserted into the APC and c-myc genes leading to
mutation and cause development of some colon or breast
cancer.

16. Conti…..
A type of SINE called Alu elements integrated into the
BRCA2 gene and inactivate this tumor- suppresser gene
and lead to breast cancer.

17. Potential effect of transposons on the genome-
EFFECT CAUSE
Gene mutation or inactivation Insertion into coding region or intron of a gene or inaccurate
excision from the coding region of a gene
change in gene regulation Alteration in splicing or alteration in transability of mRNA
Gene duplication Replication of a trasposon
Gene deletion Recombination between two transposons
Chromosome breakage Excision of a transposon, followed by an inadequate DNA repair
Chromosome rearrengemet Recombination between transposon located at two different places

18. APPLICATION OF TE
-Use as cloning vehicle.
-Provide raw material for evolution.
-Drug resistance transposones are useful in development of
plasmid as cloning vehicles.
--Use of transposones to increase the rate of mutation due to
insertional inactivation.