Jan 27, 2013 | The Health Matrix | Gabriela Segura MD.
"Junk" DNA includes a whole subset of names such as introns, retrotransposable elements, and non-coding RNAs (ncRNAs). In fact, ncRNAs are often located near genes known to be important to both stem cells and cancer, to serve as enhancer elements which promote their gene expression. Stem cells are the cells that have the potential to turn into lots of other cells. So this junk DNA can influence how stem cells specifically differentiate into multiple cell types.
In fact, it is now estimated that 80% of our genome is biologically active with only 1% of our genome encoding for proteins:
Junk DNA Not Junk After AllThat was known for some time, but it is now official since September 2012 or so. Evolutionary speaking, it makes a lot of sense...
A staggering batch of over 30 papers published in Nature, Science, and other journals this month, firmly rejects the idea that, apart from the 1% of the human genome that codes for proteins, most of our DNA is "junk" that has accumulated over time like some evolutionary flotsam and jetsam.The papers, representing 10 years of work of the ENCODE ("Encyclopedia of DNA Elements") project, completed by hundreds of scientists from dozens of labs around the world, reveal that 80% of the human genome serves some purpose and is biochemically active, for example, in regulating the expression of genes situated nearby.
Viral "Junk" DNA
The greatest shock of genomic science was to find that the human genome contains more viral than "human" genes. That is, the human genome is made from thousands of viruses that infected our distant ancestors. They got there by infecting eggs or sperm, inserting their own DNA into ours.
Viruses are peculiar things that at a zoomed-in level may look very pretty or downright creepy depending on the virus. A virus may have DNA or RNA and the type of genetic material depends on the function and nature of the virus. Some are very infectious, others allowed us to be alive since the gene that encodes for a protein that allows for babies to fuse to their mothers during pregnancy, is a virus gene.
Most of the genetic diversity can be found in virus genes. Scientists agree that there are some 1,000,000,000,000,000,000,000,000,000,000 viruses in the ocean and it matches almost nothing to any gene from any microbe, animal, plant or other organism, even from any other known virus.
All living things have hundreds or thousands of genes imported by viruses. There are a group of viral species known as retroviruses which insert their genetic material into the host cell's DNA. When the host cell divides, it copies the virus's DNA along with its own. Retroviruses have "on switches" that prompt their host cell to make proteins out of nearby genes. Sometimes their switches turn on host genes that ought to be kept shut off, and cancer can result. This is precisely what our junk DNA - ncRNA- seems to be doing "next" to genes that have to do with stem cells and cancer cells.
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