File:Deoxyribonucleic acid (DNA).png
Deoxyribonucleic acid (DNA)
Deoxyribonucleic acid (DNA) is one of the three important macromolecules essential for life and life-processes. DNA carries genetic information as a sequence of nucleotides. A nucleotide is composed of a nucleobase (guanine, adenine, thymine or cytosine), a backbone chain of five-carbon sugar (either ribose or 2-deoxyribose), and one or more phosphate groups. Most of the DNA molecules are double-stranded helices and the two strands run in opposite directions to each other. The sequence of these four nucleobases along the backbone chain encodes the genetic information. DNA is a long polymer made from repeating units of nucleotides. The DNA molecule may be circular or linear, and can be composed of 100,000 to over 3,750,000,000 nucleotides in a long chain. DNA usually occurs as linear chromosomes in eukaryotes and is tightly and orderly packed in the process called DNA condensation to fit the small available volumes of the cell.
Only a fraction of the total sequence of the genome encodes protein. In human beings protein-coding exons are a mere 1.5% of the genome. Moreover more than 50% of DNA is in repetitive sequences and is non-coding. Complexes of structural proteins hold the DNA in chromosomes and organize the DNA into a compact structure called chromatin.
Related pictures & information
|Description||Static thumb frame of Animation of the structure of a section of DNA.|
|Date||20 March 2009|
|Source||Author: file originally uploaded by Richard Wheeler (Zephyris) at en.wikipedia|
|Pemission||This original file is licensed under the Creative Commons Attribution ShareAlike 3.0 License. In short: you are free to share and make derivative works of the file under the conditions that you appropriately attribute it, and that you distribute it only under a license identical to this one.Official license This modified file is also released under the above terms by the User:Mahmood.|
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|current||19:05, 22 November 2012||135 × 135 (9 KB)||Mahmood|
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