Mitochondrial DNA
Deborah Smith
BIOL 1406: Susan DeSessa
December 1, 2010
Mitochondrial DNA
What is mitochondrial DNA? Just as it sounds, it is a double-stranded DNA molecule located in mitochondria organelles within eukaryotic cells. Another way to express this type of DNA as used by many biologists is mtDNA. Such DNA is, at least in most multicellular organisms, maternally inherited by both the male and female offspring. (Strachan, 1999) In other words, this DNA is provided strictly by the “mother” of the offspring, and is inclusive in such species as most animals, most plants, and even fungi. While mtDNA exists in sperm, its failure to enter the egg may be related, either directly or indirectly, to its relative location in the tail of the sperm, which is more often lost during fertilization. An even more interesting aspect of the sperm mtDNA is the development of the idea that this paternal mitochondria carries with it specific markers, or ubiquitin, that allows the embryo to later select and destroy the paternal patterns. (Coble, 2006)
Packed with genetic information, mitochondrial DNA is 16,569 bp (base pairs) in length, containing 37 total genes. (Strachan) Of these 37 genes, 13 encode for polypeptides that will ultimately be used in the mitochondrial function of respiratory complexes, specifically oxidized phosphorylation to produce ATP. (Strachan) The remaining 24 genes code for the RNA molecules that are involved in the synthesis of proteins. (Twyman, 2003)
While the discovery of the mitochondria in cells occurred in 1950 by Sjostrand Palade, it was not until 1961 that M.M.K. and S. Nass discovered the DNA within. (Mitochondria Research Society, 2004) It then took another 20 years before human mtDNA was first sequenced in the Cambridge, England laboratory of Frederick Sanger in 1981, respectively called the Cambridge Reference Sequence. (Coble) However, upon further analysis, a revised Cambridge Reference Sequence was established in 1999, which is the standard typically accepted today. (Coble) Figure 1 below illustrates a section of the revised Cambridge Reference Sequence (rCRS) of the human mtDNA. Moreover, some genes that are contained in mtDNA are MT-ATP6 (ATP synthase 6), MT-ND1 (NADH dehydrogenase 1), and MT-ND4 (NADH dehydrogenase 4), which are interesting because they relate to the proteins and production of ATP include in the overall function of the mitochondria. (U.S. National Library of Medicine, 2010)
-228600205740Figure 1 (Mitoweb, n.d.)
00Figure 1 (Mitoweb, n.d.)
1 gatcacaggt ctatcaccct attaaccact cacgggagct ctccatgcat ttggtatttt
61 cgtctggggg gtatgcacgc gatagcattg cgagacgctg gagccggagc accctatgtc
121 gcagtatctg tctttgattc ctgcctcatc ctattattta tcgcacctac gttcaatatt
181 acaggcgaac atacttacta aagtgtgtta attaattaat gcttgtagga cataataata
241 acaattgaat gtctgcacag ccActttcca cacagacatc ataacaaaaa atttccacca
301 aaccccccct CCCCCgcttc tggccacagc acttaaacac atctctgcca aaccccaaaa
361 acaaagaacc ctaacaccag cctaaccaga tttcaaattt tatcttttgg cggtatgcac
421 ttttaacagt caccccccaa ctaacacatt attttcccct cccactccca tactactaat
481 ctcatcaata caacccccgc ccatcctacc cagcacacac acaccgctgc taaccccata
541 ccccgaacca accaaacccc aaagacaccc cccacagttt atgtagctta cctcctcaaa
601 gcaatacact gaaaatgttt agacgggctc acatcacccc ataaacaaat aggtttggtc
661 ctagcctttc tattagctct tagtaagatt acacatgcaa gcatccccgt tccagtgagt
721 tcaccctcta aatcaccacg atcaaaaggA acaagcatca agcacgcagc aatgcagctc
781 aaaacgctta gcctagccac acccccacgg gaaacagcag tgattaacct ttagcaataa…
BASE COUNT (16568 total): 5124 a 5181 c 2169 g 4094 t
Many studies are currently being conducted in the matter of the human genome today. One such example would include the Human Genome Project, which has made drastic strides in not only the mapping of the human genome, but also the suggestion of an epigenome.
Understanding mitochondrial DNA may aid in the understanding the inheritance of many genetic conditions, including some cancers, cyclic vomiting syndrome, and Leber hereditary optic neuropathy. (U.S. National Library of Medicine) One characteristic of mtDNA suggesting its significance is that it has a high copy number, meaning that multiple copies of this hereditary information exist per mitochondria, per cell. (Coble) While mtDNA may not be unique to one individual, it holds a great significance in such scientific fields as forensics, as even a highly degraded specimen, or a low quantity sample, may still produce a multitude of mtDNA that can be recovered and analyzed for identifying purposes. Some examples of this would include hairs that do not have an attached root or tissue, aged or mummified remains, and even teeth. (Coble) Overall, mitochondrial DNA holds a great deal of inheritable information, as passed on from mother to offspring in a variety of species. Understanding this concept, and gaining the knowledge of our ancestry, will go a long way in analyzing the affects mtDNA holds over inheritable factors and will provide an insight into the potential causes of certain disorders and diseases, thus allowing for a path to discovering preventive techniques.
References
Coble, M. (2006). Mitochondrial DNA Workshop. Web. Retrieved December 1, 2010. <http://www.cstl.nist.gov/biotech/strbase/pub_pres/Coble_mtDNAworkshop_Mar2006a.pdf>
Mitochondria Research Society. (2004). Mito Time Line. Web. Retrieved December 1, 2010. <http://www.mitoresearch.org/timeline.html>
Mitoweb. (n.d.) Revised Cambridge Reference Sequence (rCRS) of the Human Mitochondrial DNA. Web. Retrieved December 1, 2010. <http://www.mitomap.org/bin/view.pl/MITOMAP/HumanMitoSeq>
Strachan, T. (1999). Chapter 7: Organization of the Human Genome. National Center for Biotechnology Information. Web. Retrieved December 1, 2010. <http://www.ncbi.nlm.nih.gov/books/NBK7587/>
Twyman, R. (2003). The Mitochondrial Genome. The Human Genome. Web. Retrieved December 1, 2010. <http://genome.wellcome.ac.uk/print/WTD020740_print.html>
U.S. National Library of Medicine. (2010). Genetics Home Reference. Web. Retrieved December 1, 2010. <http://ghr.nlm.nih.gov/chromosome/MT/show/print>
