1. GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND
TECHNOLOGY
TOPIC : P ELEMENT - TRANSPOSON
NAME OF THE STUDENT : ANKIT GHOSH
UNIVERSITY ROLL NUMBER : 31308421036
ACADEMIC SESSION : 2022-2023
PAPER NAME : MICROBIAL GENETICS
PAPER CODE : CMc 301
Maulana Abul Kalam Azad University of Technology
2. INTRODUCTION
B. Sc./ SEM 3/2022-23/ / MICROBIAL GENETICS / CMc 301 /Presentation_1
P elements are cut-and-paste transposons in the genomes of Drosophila
melanogaster and several other Drosophila species. The transposition of these elements
is catalyzed by an enzyme, the transposase, which is encoded by the structurally
complete members of the P-element family.
• The transposon is responsible for the P trait of the P element and it is found only in wild
flies. They are also found in many other eukaryotes.
• The P element - a transposon was discovered in D. melanogaster in the1970s
• P elements are transposable elements that were discovered in Drosophila as the
causative agents of genetic traits called hybrid dysgenesis.
• P elements are commonly used as mutagenic agents in genetic experiments
with Drosophila.
3. CHARACTERISTICS
B. Sc./ SEM 3/2022-23/ / MICROBIAL GENETICS / CMc 301 /Presentation_1
The P element is a class II transposon, and moves by a DNA-based "cut and paste" mechanism.
The recognition sequence comprises four exons separated by three introns.[2] Complete splicing of
the introns produces the transposase enzyme, while alternative partial splicing of introns 1 and 2,
leaving only intron 3 in the mRNA transcript, encodes the P element repressor. The complete,
autonomous P element encodes a transposase enzyme, which recognizes the 31-
bp terminal inverted repeats at either end of the P element and catalyzes P element excision and re-
insertion.
The shortest and longest P elements are non-autonomous elements. The longest P elements encode
transposase needed for transposition. The same sequence that encodes the transposase also encodes
a suppressor of transposition, which accumulates in the cytoplasm during the development of cells.
Thus, in a cross of a P or M male with a P female, the female cytoplasm contains the suppressor,
which binds to any P elements and prevents their transposition.
4. B. Sc. / SEM 3/2022-23/ / MICROBIAL GENETICS / CMc 301 /Presentation_1
The P element from Drosophila has many characteristics of a transposable sequence capable of
regulating its transposition, and it too can be engineered for transformation of DNA into cells.
When a male P+ line is mated with a female non-P line, a short interval of intense transposition in
the developing embryo follows, and many genes are inactivated by the insertion of P elements.
Afterwards, the transposition activity ceases, and the resultant strains are genetically stable. The
reverse–mating a P+ female with a non-P male–does not stimulate transposition. By analogy to the
bacterial transposons or to phage lambda, the P elements behave as though they encode a repressor
and enzymes necessary for transposition. Upon entry of a P element into a new cytoplasm, the
temporary absence of repressor permits the transposition enzymes to be synthesized, and
transposition likely occurs. Additionally, the Drosophila P elements appear to be stimulated to
excise from their former locations as well as to copy themselves into new locations because many
of the mutations generated by insertions of P elements can be induced to revert by the same mating
process that stimulates P element mutations.
A P element would form a useful vector for inserting DNA into a chromosome of a fruit fly. By
analogy with the bacterial transposons, nearly any sequence of foreign DNA could be inserted into
the middle
5. CONCLUSION
SUMMARY
B. Sc./ SEM 3/2022-23/ / MICROBIAL GENETICS / CMc 301 /Presentation_1
P elements have been useful research tools in other ways as well. For example, specially
modified P elements can be used to determine the expression pattern of nearby genes. These
‘enhancer traps’ carry a reporter gene (i.e., a gene whose expression is easily monitored)
whose promoter responds to genomic regulatory elements (‘enhancers’) close to its insertion
site. By examining the expression pattern of a collection of such insertions, researchers can
identify genes with a particular time and place of expression during development.
The study of DNA repair has also been aided by P elements. As mentioned above, P element
excision results in a double-strand DNA break which is then repaired by one of several
mechanisms. The products of these repair events are easily recovered to provide information
on the repair process.
6. REFERENCE
B. Sc. / SEM 3/2022-23/ / MICROBIAL GENETICS / CMc 301 /Presentation_1
•eland Hartwell et al.. 2004. Genetics - From Genes to Genomes 2nd Edition. McGraw-Hill
•Engels, W. R. P Elements in Drosophila
1.^ Majumdar, S; Rio, DC (April 2015). "P Transposable Elements in Drosophila and other Eukaryotic
Organisms". Microbiology Spectrum. 3 (2): MDNA3–0004–2014. doi:10.1128/microbiolspec.MDNA3-0004-
2014. PMC 4399808. PMID 26104714.
2.^ Jump up to:a b Griffiths, A. J. (2005). An introduction to genetic analysis. Macmillan.
3.^ Brennecke, J.; et al. (2008). "An epigenetic role for maternally inherited piRNAs in transposon
silencing". Science. 322 (5906): 1387–
1392. Bibcode:2008Sci...322.1387B. doi:10.1126/science.1165171. PMC 2805124. PMID 19039138.
