Handout #1: "Junk DNA"

News Report (Science Newsette)

"What you thought was junk DNA may be as precious as your own life"

by S. Catherine Silver Key

Almost half of all diseases are caused by mutations in portions of genes considered "junk DNA". These pieces of DNA are considered to be responsible for some conditions and diseases as cancer, cystic fibrosis, and thalassemia. This occurs since genes are made of DNA that is transcribed into RNA (pre-mRNA) in the nucleus. Before this mRNA leaves the nucleus to be translated into protein, it must undergo some alterations, such as the removal of portions f pre-mRNA. This genetic code is spliced to make the correct mRNA and the subsequent protein. The "junk"left behind in the nucleus is referred to as introns. on the other hand, the portions that are spliced to form mRNA are allowed to exit the nucleus and are referred to as exons. the exon-containing mRNA encodes the protein-to-be. mRNA must be spliced correctly in order to avoid mistakes in the final product. Without this, the protein product will be defective. This is what happens in about 50% of all genetic diseases.

(Written on April 4th, 2008)