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Junk DNA

Junk DNA (non-functional DNA) is a controversial term referring to types of Non-Coding DNA[1] that is considered obsolete by many scientists[2]. This term traditionally refers to parts of the DNA sequence that do not code for proteins, and thus were once assumed to not have relevant biological functions. The concept of "Junk DNA" is thought to have held back investigation of these sections of the genetic code, which appear to perform an important role in evolution.[2] According to researchers working on the 'ENCODE' project, a good deal of what is called ‘junk DNA’ "is actually a massive control panel with millions of switches regulating the activity of our genes. Without these switches, genes would not work"[2]

Most organisms have some DNA that has been considered 'junk' in their genomes—mostly pseudogenes and fragments of transposons and viruses—but it is possible that some organisms have substantial amounts of junk DNA.[3]

All protein-coding regions of genes are generally considered as functional elements in genomes. Additionally, non-protein coding regions such as genes for ribosomal RNA and transfer RNA, regulatory sequences controlling expression of those genes, elements of the genome involving origins of replication (in all species), centromeres, telomeres, and scaffold attachment regions (in eukaryotes) are generally considered as functional elements of genomes as well. (See Non-coding DNA for more information.)

It is difficult to determine whether other regions of the genome are functional or nonfunctional. There is considerable controversy over which criteria should be used to identify function. Many scientists have an evolutionary view of the genome and they prefer criteria based on whether DNA sequences are preserved by natural selection.[4][5][6] Other scientists dispute this view or have different interpretations of the data.[7][8][9]

  1. ^ Fagundes NJ, Bisso-Machado R, Figueiredo PI, Varal M, Zani AL (May 10, 2022). "What We Talk About When We Talk About "Junk DNA"". Genome Biology and Evolution. 14 (5): evac055. doi:10.1093/gbe/evac055. ISSN 1759-6653. PMC 9086759. PMID 35535669.
  2. ^ a b c Magazine S, Eveleth R. "Junk DNA Isn't Junk, and That Isn't Really News". Smithsonian Magazine. Retrieved July 30, 2024.
  3. ^ Gil R, and Latorre A (2012). "Factors behind junk DNA in bacteria". Genes. 3 (4): 634–650. doi:10.3390/genes3040634. PMC 3899985. PMID 24705080.
  4. ^ Ohno S (1972). "An argument for the genetic simplicity of man and other mammals". Journal of Human Evolution. 1 (6): 651–662. doi:10.1016/0047-2484(72)90011-5.
  5. ^ Morange M (2014). "Genome as a Multipurpose Structure Built by Evolution" (PDF). Perspectives in Biology and Medicine. 57 (1): 162–171. doi:10.1353/pbm.2014.0008. PMID 25345709. S2CID 27613442.
  6. ^ Palazzo AF, Kejiou NS (2022). "Non-Darwinian Molecular Biology". Front. Genet. 13: 831068. doi:10.3389/fgene.2022.831068. PMC 8888898. PMID 35251134.
  7. ^ Germain PL, Ratti E, and Boem F (2014). "Junk or functional DNA? ENCODE and the function controversy". Biology & Philosophy. 29 (6): 807–821. doi:10.1007/s10539-014-9441-3. S2CID 254277794.
  8. ^ Mattick JS (2023). "RNA out of the mist". Trends in Genetics. 39 (3): 187–207. doi:10.1016/j.tig.2022.11.001. PMID 36528415. S2CID 254768457.
  9. ^ Kellis M, Wold B, Snyder MP, Bernstein BE, Kundaje A, Marinov GK, et al. (April 2014). "Defining functional DNA elements in the human genome". Proceedings of the National Academy of Sciences of the United States of America. 111 (17): 6131–6138. Bibcode:2014PNAS..111.6131K. doi:10.1073/pnas.1318948111. PMC 4035993. PMID 24753594.

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