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In the 1950s, Barbara McClintock published groundbreaking research on maize with broken chromosomes and characteristic DNA elements.[1] These DNA elements could switch positions, turn on and off, and reverse mutations between generations of the Zea Mays plant. The article, “Induction of Instability at Selected Loci in Maize,” won her the Nobel prize in 1983.[2] Ninety percent of maize DNA is transposable elements.[3] Transposons, transposable elements, or jumping genes, are DNA sequences that can change their position in the genome. Genomes are the comprehensive set of genes in an organism. Transposons get their name from their mode of movement, called transposition. Transposition is often simplified to a “cut-and-paste” mechanism of movement through the genome. A transposon could, for example, be cut from its position on chromosome 9 and pasted into a new position on chromosome 11. Because of the nature of transposition, the process leads to mutation and changes in the amount of DNA in a cell. They are responsible for a large number of mutations and genetic polymorphisms, a significant contribution to genetic diversity.[1]

Transposon insertions can be pathogenic, being able to alter gene expression; transposon inserts represent about 5% of the molecular pathology. Among the alterations in the function of the transposons, we find the: Kindler syndrome (in the FERMT1 gene or fermitin family member 1); hemophilia A (in the factor VIII gene or anti-hemophiliac factor or AHF). Transposon inserts may play a role in determining susceptibility to multifactorial diseases such as tumors. Transposons, and real disease mutations, seem to be able to create hypomorphic alleles: they are not actual pathogenic alleles but alleles with reduced functionality that can worsen the phenotype when they are in association with a mutation- real disease. These hypomorphic alleles may have some weight in generating traits of susceptibility to multifactorial diseases.