What is retrotransposon?

Anton Scott Goustin asg at cmb.biosci.wayne.edu
Wed Jul 19 22:42:15 EST 1995


BANANA & PLANTAIN <N.C.Pancholi at reading.ac.uk> wrote:
>
>Hello Netters,
>Can anybody described in brief retrotransposon?
>Also, is it possible to use retrotrasnposon mediated fingerprinting to
>assess the magnitude of somaclonal variation?
>
>Thanks.
>
>-Naresh
>
>
>-------------------------------------------------------------------------
>      NARESH PANCHOLI
>      AGRICULTURAL BOTANY            PHONE: +44 1734 875123 EXT. 4087
>      SCHOOL OF PLANT SCIENCES       FAX:   +44 1734 316577
>      UNIVERSITY OF READING
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>      ENGLAND                                   N.C.PANCHOLI at READING.AC.UK
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>
A retrotransposon (or retroposon) is a piece of DNA integrated into a chromosome after being created by the action of RNA-directed DNA polymerase (reverse transcriptase) on a cellular RNA.  Examples are the LINES elements in human chromosomes; there are 100,000 copies of these elements.  A few are full-length transcription units, complete with promoter, and two intact open reading frames (ORFs).  Very occasionally, the TU is transcribed into an RNA which can occasionally be translated into the encoded proteins.  One of the ORFs encodes a reverse transcriptase; the RT can convert the RNA into a dsDNA.  The dsDNA can--very rarely--be re-integrated into a new chromosomal site, and--even more rarely--stably integrate.  Even more rarely, the stable integration is in the germline, and can thus be passed to new offspring.  Rarely, but it happens.  Haig Kazazian described a case a few years back where a retroposon came to be situated in one family in one of the copies of the gene for the clotting factor, Factor XIII.  Factor XIII deficiency leads to hemophilia.  Thus, retroposon transposition (movement from one chromosomal site to another) can occur in the germline of humans, albeit very very rarely.  ´Jumping genesª jump, but rarely!





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