jumping gene transposable element transposition transposon

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Transposable element transposon Inverted repeats, palindrome transposase

Direct repeats

Tn5: Kan r Tn10: Tet r

Replicative transposition: Tn3

nonreplicative transposition: Tn10

Maize Barbara McClintock Figure 23.9

Retrotransposons retroviruses

RNase H degrades the RNA part of an RNA-DNA hybrid

LTR-containing retrotransposons Copia of Drosophila: 1% of the total fruit fly genome Ty of yeast Human endogenous retroviruses: 1-2% of the genome

Non-LTR retrotransposons long interspersed elements (LINES) L1: 17% of the human genome EN: endonuclease RT: reverse transcriptase

Nonautonomous retrotransposons encode no protein Alu elements contain the sequence AGCT that is recognized by the restriction enzyme AluI. They are present in up to a million copies in the human genome. They can not transpose by themselves. Instead they take advantage of the retrotransposition machinery of other elements, such as LINEs.

retrohoming

retrotransposition of group II intron