junk DNA


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junk DNA

that portion of DNA that is not transcribed and expressed, comprising a major fraction of the base pairs of the human genome; much of this DNA is repetitive in seuqence and appears to serve no purpose; its function is not known. segments of DNA that appear to serve no function and are replicated along with the rest of the DNA that serves vital functions; examples are pseudogenes and tandemly repeated DNA sequences that seem functionless but are retained by unequal crossing-over.
Synonym(s): selfish DNA

junk DNA

n.
A DNA sequence that is part of a genome and is not known to code for proteins or to regulate the expression of genes. Junk DNA may constitute up to 95 percent of the human genome and is postulated to be involved in the evolution of new genes and possibly the repair of genes.
Any long stretch of non-protein-coding DNA that composes 97–98% of the human genome, which has been highly conserved in plant and animal genomes over millions of years. It is now recognised that non-coding DNA determines the differences in transcription rates of genes, which is what makes each of us unique, making junk DNA is a misnomer

junk DNA

(jŭngk)
The portion of DNA that is not transcribed and expressed, comprising about 90% of the 3 billion base pairs of the human genome; its function is not known.
Synonym(s): selfish DNA.

junk DNA

The long sequences of DNA between those segments that code for protein. Only three percent of DNA consist of functional genes. The rest is junk DNA and is preserved over millions of years of evolution. Species differ not so much in the number of active genes as in the amount of junk DNA. These facts suggest the junk DNA has an important function, not yet discovered.

junk DNA

DNA of no apparent function, generally in GENOMES ofEUKARYOTES, where sequences have been repeated. Also called non-coding DNA.
References in periodicals archive ?
Junk DNA is that which has not formed genes and it accounts for almost half of an individual's genetic material, built up over millions of years through evolution.
This so-called junk DNA has largely been pushed aside and neglected in the wake of genomic gene discoveries, the UCSF scientists said.
For most scientists the interest in junk DNA is limited to recognizing it so that they can focus on the remaining, potentially functional regions, but several key findings came out of analyzing the repetitive DNA in mouse.
Yet this variation occurs in a region of DNA far from any protein-encoding genes, in an area of so-called junk DNA that scientists once presumed to have no function.
Even more surprisingly, the junk DNA may not be junk after all.
Most of the human genome is so-called junk DNA, which contains no code for proteins and was long thought to be useless.
Most SNPs occur in places in the genome that aren't used for making proteins--the so-called junk DNA.
The mammalian genome might have a good mason to hold on to its vast collection of what scientists call junk DNA.
The researchers found that more than 1500 genes that were expressed in the uterus solely in the placental mammals and that the expression of these genes in the uterus is coordinated by transposons, which are essentially selfish pieces of genetic material that replicate within the host genome and used to be called junk DNA.
And the mouse's smaller number of base pairs may simply stem from that animal's ridding its genome more effectively of so-called junk DNA sequences than humans did.
This accounts for large chunks of duplicated sequences--often called junk DNA.
Supporting a theory proposed 2 years ago, a research team has uncovered evidence that DNA sequences usually dismissed as junk DNA without any function actually help determine what genes on the X chromosome become suppressed.