Transposons are sequences of DMA that can move around to different positions within the genome of a single cell, aprocess called transposition. In the process, they can cause mutations and change the amount of DNA in the genome.Transposons are also called "jumping genes" or "mobile genetic elements".

Discovered by Barbara McClintock early in hecareer, the topic went on to be a Nobel winning work in 1983.There are a variety of mobile genetic elements, and they canbe grouped based on their mechanism of transposition. Class I mobile genetic elements, or retrotransposons. move in thegenome by being transcribed to RNA and then back to DNA by reverse transcriptase, while class II mobile geneticelements, or DNA transposons move directly from one position to another within the genome using a transposase to "cutand paste" them within the genome.

Transposons are very useful to researchers as a means to alter DNA inside of a livingorganism. Transposons make up a large fraction of genome sizes which is evident through the C-values of eukaryoticspecies. As an example about 45% of the human genome is composed of transposons and their defunct remnants.Both classes oftransposon may lose their ability to synthesise reverse transcriptase or transposase through mutation, yecontinue to jump through the genome because other transposons are still producing the necessary enzyme.Transposons are mutagens.

They can damage the genome of their host cell in different ways:* Atransposon or a retroposon that inserts itself into a functional gene will most likely disable that gene.* After a transposon leaves a gene, the resulting gap will probably not be repaired correctly.* Multiple copies of the same sequence, such as Alu sequences can hinder precise chromosomal pairing duringmitosis, resulting in unequal crossovers, one of the main reasons for chromosome duplication.Diseases that are often caused by transposons include hemophilia A and B, severe combined immunodeficiency,porphyria, predisposition to cancer, and Duchenne muscular dystrophy..

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