New finding ‘challenges current assumptions’ about jumping genes

June 12th, 2009 - 3:01 pm ICT by ANI  

Washington, June 12 (ANI): Challenging standard assumptions about mobile DNA, or the so-called jumping genes, scientists have found that such genes do most of their jumping not during the development of sperm and egg cells, but during the development of the embryo itself.

Jumping genes - also called transposons - are sequences of DNA that can move or jump to different areas of the genome within the same cell, and can be a rare cause of certain diseases like hemophilia and Duchenne muscular dystrophy.

In addition, transposon insertion into the genome could play a role in the development of cancer.

However, it’s not known how frequently diseases due to insertions can be inherited in the next generation.

The current work alters the current thinking that mobile DNA inserts only in eggs and sperm during their respective early development.

“(The research) challenges standard assumptions on the timing of when mobile DNA, so-called jumping genes, insert into the human genome,” said senior author Dr. Haig H. Kazazian Jr., Seymour Gray Professor of Molecular Medicine in Genetics at the University of Pennsylvania School of Medicine.

In the study, they looked at retrotransposons, one class of jumping genes, with the L1 family the most abundant type of retrotransposon in the human genome.

The L1 family of retrotransposons comprises about 17 percent of the human genome.

The researchers found that insertions took place during embryogenesis after fertilization, at a time when nearly all of the changes can’t be inherited.

Based on the study’s findings, the researchers have now claimed that many of those insertions occur in the early embryo, perhaps in the 4- or 8-cell stage.

The study has been published this month in Genes and Development. (ANI)

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