News tagged with junk dna
In evolutionary biology and molecular biology, junk DNA is a provisional label for the portions of the DNA sequence of a chromosome or a genome for which no function has been identified. The term was introduced in 1972 by Susumu Ohno, but is as of 2008 somewhat outdated, being used mainly in popular science and in a colloquial way in scientific publications. For some sequences once classified as junk DNA, functions have been found, and others are subject to ongoing research. About 95% of the human genome has once been designated as "junk", including most sequences within introns and most intergenic DNA. While much of this sequence may be an evolutionary artifact that serves no present-day purpose, some junk DNA may function in ways that are not currently understood. Moreover, the conservation of some junk DNA over many millions of years of evolution may imply an essential function. Some consider the "junk" label as something of a misnomer, but others consider it appropriate as junk is stored away for possible new uses, rather than thrown out; others prefer the term "noncoding DNA" (although junk DNA often includes transposons that encode proteins with no clear value to their host genome). About 80% of the bases in the human genome may be transcribed, but transcription does not necessarily imply function.
Broadly, the science of functional genomics has developed widely accepted techniques to characterize protein-coding genes, RNA genes, and regulatory regions. In the genomes of most plants and animals, however, these together constitute only a small percentage of genomic DNA (less than 2% in the case of humans). The function, if any, of the remainder remains under investigation. Most of it can be identified as repetitive elements that have no known biological function for their host (although they are useful to geneticists for analyzing lineage and phylogeny). Still, a large amount of sequence in these genomes falls under no existing classification other than "junk". For example, recent experiments removed 1% of the mouse genome and were unable to detect any effect on the phenotype. This result suggests that the DNA is nonfunctional. However, it remains a possibility that there is some function that the experiments performed on the mice were merely insufficient to detect. This can also be evidence for reconstructing ancestral lineages.
While overall genome size, and by extension the amount of junk DNA, are correlated to organism complexity, there are many exceptions. For example, the genome of the unicellular Amoeba dubia has been reported to contain more than 200 times the amount of DNA in humans".
The pufferfish Takifugu rubripes genome is only about one tenth the size of the human genome, yet seems to have a comparable number of genes. Most of the difference appears to lie in what is now known only as junk DNA. This puzzle is known as the C-value enigma or, more conventionally, the C-value paradox.
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(Medical Xpress)—Specific DNA once dismissed as junk plays an important role in brain development and might be involved in several devastating neurological diseases, UC San Francisco scientists have found.
Genetics Apr 15, 2013 | 4.9 / 5 (14) | 2 |
A decade after completion of the Human Genome Project on April 14, 2003, a top official of the National Institutes of Health surveyed the rarefied view from that mountaintop:
Genetics Apr 15, 2013 | not rated yet | 0
A controversy at last: most of our DNA is junk, no it isn't, yes it is. Actually, I think it is – up to 90% really is junk.
Genetics Mar 15, 2013 | 4.5 / 5 (4) | 1
Whitehead Institute researchers have identified a previously unrecognized layer of genetic regulation that is necessary for the generation of undesirable white fat cells. When this regulation is disrupted, white fat cells ...
Overweight and Obesity Feb 13, 2013 | 5 / 5 (2) | 0 |
In September 2012, the Encyclopedia of DNA Elements (ENCODE) Project Consortium, a multi-institution collaboration that included the Broad Institute, capped off nine years of research with a flurry of papers ...
Genetics Jan 07, 2013 | 5 / 5 (1) | 0
Once considered unimportant "junk DNA," scientists have learned that non-coding RNA (ncRNA) RNA molecules that do not translate into proteins play a crucial role in cellular function. Mutations in ncRNA are ...
Medical research Apr 24, 2012 | not rated yet | 1 |
A team of researchers at Case Western Reserve University School of Medicine have identified a new mechanism by which colon cancer develops. By focusing on segments of DNA located between genes, or so-called "junk DNA," the ...
Genetics Apr 12, 2012 | 5 / 5 (8) | 0 |
An international research team led by Weill Cornell Medical College investigators have discovered two inherited-genetic deletions in the human genome linked to development of aggressive prostate cancer. The findings, published ...
Cancer Apr 09, 2012 | 5 / 5 (1) | 0 |