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Encyclopedia > P element

A P element is a transposon that is present in the fruit fly Drosophila melanogaster and is used widely for mutagenesis and the creation of genetically modified flies used for genetics research. The P element causes a phenotype known as hybrid dysgenesis. They seem to have first appeared in the species only in the middle of the twentieth century. Within 50 years, they have spread through every wild population of the species, so that only older laboratory stocks lack them. Transposons are sequences of DNA that can move around to different positions within the genome of a single cell, a process called transposition. ... Binomial name Drosophila melanogaster Meigen, 1830 Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a dipteran (two-winged) insect, and is the species of fruit fly that is most commonly used in genetic experiments; it is among the most important model organisms. ...

Contents

Characteristics

The P element is a class II transposon, which means that its movement within the genome is made possible by a transposase. The complete element is 2907 bp and is autonomous because it encodes a functional transposase; non-autonomous P elements which lack a functional transposase gene due to mutation also exist. Non-autonomous P elements can still move within the genome if there are autonomous elements to produce transposase. The P element can be identified by its terminal 31-bp inverted repeats, and the 8 bp direct repeats in movement into and out of DNA sequence produces. Transposase is an enzyme that binds to single-stranded DNA and can incorporate it into genomic DNA. Class I transposons encode a transposase which allows them to enable transposons to be cut from genomic DNA and be inserted at another location. ... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ...


Hybrid dysgenesis

Hybrid dysgenesis refers to the high rate of mutation in germ line cells of Drosophila strains resulting from a cross of males with autonomous P elements (P Strain/P cytotype) and females that lack P elements (M Strain/M cytotype). The hybrid dysgenesis syndrome is marked by temperature-dependent sterility, elevated rates of mutation, chromosome rearrangement and recombination. This is caused by the transposition of P elements within the germ-line cells of offspring of P strain males with M strain females. This transposition only occurs in germ-line cells because a splicing event needed to make transposase mRNA does not occur in somatic cells. Germline is a word used in biology and genetics. ... In genetics, splicing is a modification of genetic information prior to translation. ... Transposase is an enzyme that binds to single-stranded DNA and can incorporate it into genomic DNA. Class I transposons encode a transposase which allows them to enable transposons to be cut from genomic DNA and be inserted at another location. ... The interaction of mRNA in a eukaryote cell. ...


The reason that hybrid dysgenesis takes place when crossing P strain males with M strain females and not when crossing P strain females (females with autonomous P elements) and M strain males is that the eggs of P strain females contain high amounts of repressor protein that prevents transcription of the transposase gene. The eggs of M strain mothers, on the other hand, do not contain the repressor protein, allowing for transposition of P elements from the sperm of fathers. Transcription is the process through which a DNA sequence is enzymatically copied by an RNA polymerase to produce a complementary RNA. Or, in other words, the transfer of genetic information from DNA into RNA. In the case of protein-encoding DNA, transcription is the beginning of the process that ultimately...


P element in molecular biology

The P element has found wide use in Drosophila research as a mutagen. The mutagenesis system typically uses an autonomous but immobile element, and a mobile nonautonomous element. Flies from subsequent generations can then be screened by phenotype or PCR. Wikipedia does not yet have an article with this exact name. ...


The most common use of the P element is for genetic modification of Drosophila. The gene of interest is created as a recombinant DNA sequence with P element insertion sequences added at the '5 and '3. A plasmid containing the sequence is then injected into a pre-blastoderm embryo in the presence of the transposase and it will transpose into the genome.


References

  • Leland Hartwell et al.. 2004. Genetics - From Genes to Genomes 2nd Edition. McGraw-Hill
  • Engels, W. R. P Elements in Drosophila

External links

  • FlyBase

  Results from FactBites:
 
P Elements in Drosophila (6407 words)
This interpretation is strengthened by the observation that when the P element resides on an extrachromosomal plasmid, and therefore lacks a sister chromatid for a template, the resulting footprints rarely contain more than four base pairs from each terminus (O'Brochta, Gomez and Handler 1991).
P elements are not normally mobile in somatic cells, and their germline mobility does not occur within P strains.
Several P element vectors are available to facilitate expression of a given gene in a particular tissue through fusion of the gene to a specific promoter.
Chemistry: WebElements Periodic Table (426 words)
The periodic "law" of chemistry recognises that many properties of the chemical elements are periodic functions of their atomic number (the number of protons within the element's atomic nucleus).
The periodic table is an arrangement of the chemical elements ordered by atomic number in columns (groups) and rows (periods) presented so as to emphasize their periodic properties.
The element polonium is very much in the news at present, perhaps for the first time ever, and for the wrong reasons.
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