Noncoding DNA

In genetics, noncoding DNA describes components of an organism's DNA sequences that do not encode protein sequences. Some noncoding DNA is transcribed into functional noncoding RNA molecules (e.g. transfer RNA, ribosomal RNA, and regulatory RNAs), while others are not transcribed or give rise to RNA transcripts of unknown function. The amount of noncoding DNA varies greatly among species. For example, fully 98% of the human genome is noncoding DNA, while only about 2% of a typical bacterial genome is noncoding DNA.

Initially, a large proportion of noncoding DNA had no known biological function and was therefore sometimes referred to as "junk DNA", particularly in the lay press. Some sequences may have no biological function for the organism, such as endogenous retroviruses. However, many types of noncoding DNA sequences do have important biological functions, including the transcriptional and translational regulation of protein-coding sequences. Other noncoding sequences have likely, but as-yet undetermined, functions (this is inferred from high levels of homology and conservation seen in sequences that do not encode proteins but, nonetheless, appear to be under heavy selective pressure).

The Encyclopedia of DNA Elements (ENCODE) project reported in September 2012 that over 80% of DNA in the human genome "serves some purpose, biochemically speaking".

Read more about Noncoding DNA:  Fraction of Noncoding Genomic DNA, Functions of Noncoding DNA, Noncoding DNA and Evolution, Junk DNA, Noncoding DNA and Long Range Correlations

Other articles related to "noncoding dna, dna, noncoding":

Deoxyribonucleic Acid - Biological Functions - Genes and Genomes
... Further information Cell nucleus, Chromatin, Chromosome, Gene, Noncoding DNA Genomic DNA is tightly and orderly packed in the process called DNA condensation to ... In eukaryotes, DNA is located in the cell nucleus, as well as small amounts in mitochondria and chloroplasts ... In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid ...
History Of Molecular Evolution - The Neutral Theory of Molecular Evolution - The Neutralist-selectionist Debate and Near-neutrality
... clock) were fairly independent of generation time, rates of noncoding DNA divergence were inversely proportional to generation time ... substitutions are slightly deleterious while noncoding DNA substitutions are more neutral ... and vice versa), but in large populations with short generation times, noncoding DNA evolves faster while protein evolution is retarded by selection (which is more ...
Noncoding DNA and Long Range Correlations
... A statistical distinction between coding and noncoding DNA sequences has been found ... It has been observed that nucleotides in non-coding DNA sequences display long range power law correlations while coding sequences do not ...
Human Genome - Noncoding DNA (ncDNA)
... Noncoding DNA is defined as all of the DNA sequences within a genome that are not found within protein-coding exons, and so are never represented within the amino acid sequence of expressed proteins ... Numerous classes of noncoding DNA have been identified, including genes for noncoding RNA (e.g ... tRNA and rRNA), pseudogenes, introns, untranslated regions of mRNA, regulatory DNA sequences, repetitive DNA sequences, and sequences related to mobile genetic elements ...

Famous quotes containing the word dna:

    Here [in London, history] ... seemed the very fabric of things, as if the city were a single growth of stone and brick, uncounted strata of message and meaning, age upon age, generated over the centuries to the dictates of some now all-but-unreadable DNA of commerce and empire.
    William Gibson (b. 1948)