Animal Mitochondrial Genome

One of the most essential organelles in the living creature cell is the chondriosome, as it is not only the center of adenosine triphosphate production, it also live with a phylo elementtic value that reveals taxonomic relationships among organisms. These argon rod-shaped organelles convert oxygen and glucose into adenosine triphosphate (adenosine triphosphate), other than kn throw as the chemic energy currency of the cell that powers the cells metabolic activities. This kind of respiration is termed oxidative and it supplies energy to most cellular activities.This mode of respiration is more economical than in the absence of oxygen as an oxidative respiration suffer only produce devil ATPs, as opposed to the 36-38 ATPs produced by the aerobic mode. This is why higher life forms be adapted to utilize oxygen for their ATP production (Davidson, 2004). Mitochondria ar hypothesized by scientist to have evolved from a dependent relationship between aerobic bacteria and primor dial eukaryotic cells (W everyace, 2005), otherwise kn avow as the endosymbiont theory. It numbers in common physiological processes such(prenominal) as metabolism, apoptosis, disease, and aging. Being the primary site where oxidative phosphorylation occurs, these double-membrane organelles atomic number 18 efficient in aerobic respiration which allows eukaryotic cells to generate the necessary amount of ATP (Chan, 2006).The mitochondrion take holds its own set of genes although most of its proteins (about 900) are synthesized within and import from the nuclear genome necessary for its respiratory function (Wallace, 2005).The genome guarded by this subcellular organelle relegate from the nuclear chromatin is otherwise referred to as the mitochondrial DNA (mtDNA). Particularly in animals, mtDNAs commonly have a closed-circular molecule, with the exception of certain classes containing linear mtDNA chromosomes (Boore, 1998).These extrachromosomal genomes contain 37 genes composed of 13 protein subunits for enzymes coding for oxidative phosphorylation, two ribosomal RNAs of mitochondrial ribosome, and 22 tRNAs for protein translation. Together with proteins and RNAS synthesized in the cytoplasm, products of these 37 genes allow the mitochondrion to possess its own system facilitating DNA transcription, translation, mRNA processing and protein translation. This circular genome is comprised of a mixture of covalently closed circular monomers and different amounts of concatenated dimers and higher oligomers (Burger et al., 2002).Genes contained in the animal mitochondrion are usually encoded on both strands. The H-strand, or the heavy strand, and the L-strand, or the light strand, are these two menti 1d strands that comprise the genome. Their names are derived from their molecular weight differences caused by their varying base spells. 12 out of the 13 protein coding genes comprise the H-strand while only the single gene left-hand(a) belongs to the L-strand . The genome also contains noncoding regions which are restricted to certain areas known as the D-Loop (Shadel and Clayton 1997).These two strands, the H-strand and the L-strand, originated within the D-Loop, or the displacement loop, region and within a clunk of five tRNA genes respectively. The entire comeback process only commences in the initiation of the H-strand tax deduction, while the L-strand lags behind. The L-strand synthesis tummy only begin when two-thirds of the H-strand synthesis across the circular genome is already completed. Therefore, only in the intiation of H-strand synthesis can mtDNA start replicating. Aside from its mentioned function, the D-Loop region is also the location of two transcriptional promoters (HSP and LSP), one for each strand of mtDNA. Synthesis of polycistronic transcripts for the expression of the majority or all of the genes encoded in each strand are directed by these promoters (Chang and Clayton, 1985).Scientists have speculated that t he mitochondria are derived from eubacterial endosymbionts. This is referable to the possession of mitochondria their own genetic material (DNA) and their own system for genetic expression. Although mitochondria are contained in species belognoing to different kingdoms, they offer enormous differences and even reveal phylogenetic relationships and distances.There are characteristic variations among the three major kingdoms Animalia, Eukaryomycota, and Plantae (including objections). Among animals, their mitochondrial genome is relatively small, having an approximate measurement between 16 and 19 kb, and are compactly ar postd as they lack introns or spacer regions. fungous mtDNAs are considerably tumescentr that animal mtDNAs. Their size is within the range of 17-176 kb and they encode more gene sequences than those of animals.It can be spy that the size range is quite vast, reflecting great variations in genome size. This is not due to coding capacities, instead it can be attr ibuted to the movement of varying sizes of introns and spacer regions. In the case of plants, the genome size range is even more multivariate as it spans 16 to 2400 kb. Its mtDNA is distinctly characterized by a wide variety of gene content and molecular structure, and the variation of the length of spacer regions and introns (Ohta et al., 1998).One of the most extensively study group are those of the protists. Their mtDNAs are considered intermediate in size with a measurement range of 6 to 77 kb. Most of protist genomes are compact having little or no non-coding regions. Although present, intergenic spacers are sparse and are generally small, with some coding regions overlapping. There is an general high niggardness of Adenine and Thymine that are particularly elevated in non-coding intergenic regions (Gray et al., 1997).Mitochondrial genome composition in vertebrates predominantly includes a standard set of genes coding for 13 inner mitochondrial membrane proteins for electro n transport and oxidative phosphorylation functions. Included genes for this function are nad1-6 and 4L, cob, cox1-3 and atp6 and 8. Genes for both large subunit (LSU) and small subunit (SSU) rRNAs are also contained within the animal mitochondrial genome.The mentioned set of mtDNA-encoded genes (plus atp9) is also found in fungal organisms such as Allomyces macrogynus mtDNAs. However, particular ascomycete fungi such as Schizosaccharomyces pombe lack all nad genes. Both animal and fungal mtDNAs do not encode a 5S rRNA nor, with the exception of rps3 in A. macrogynus mtDNA, do they carry any ribosomal protein genes. Terrestrial plants contain mitochondrial genomes with a a few(prenominal) extra respiratory chain protein genes such as nad9 and atp1 in M.polymorpha. besides the most distinct variation of the plant mtDNA from the animal and fungal mtDNAs is the presence of both the 5S rRNA (Gray et al., 1997).Animal mtDNA sequences are found to evolve rapidly however they maintain th eir genetic arrangements for long periods of evolutionary time. A notable example is the same arrangement of humans and trouts. Although there are few exceptions, gene arrangements are considered stable within major taxonomic groups but are variable between them. We can potentially utilize these data comparisons in accommodate phylogenetic conflicts. Greater differences would entail divergence among the taxa. Comparisons of mitochondrial gene arrangements have provided convince phylogenies in several cases where all other data were equivocal, including the relationships among major groups of echinoderms and arthropods (Burger et al., 2002).Although studies in mitochondrial genomes of different taxonomic groups are still inconclusive, it still holds a large potential in revolutionizing the taxonomic field. It has opened avenue for prospective discoveries on the currently unknown areas of biological sciences. Therefore, mitochondrial genome research studies are yet to piss their p innacle and would surely still be an essential focus of phylogenetic sciences.BibliographyBoore, J.L. (1998) Animal Mitochondrial Genomes. Nucleic Acids Research. 27 (8), 1999, pp.1767-1780.Burger, G., Forget, L., Zhu, Y., Gray, M.W., and Lang, B.F. (2002) Uniquemitochondrial genome architecture in unicellular relatives of animals. PNAS, 100 (3), 04 February, pp. 892-897.Chan, D.C. (2006) Mitochondria propulsive Organelles in Disease, Aging, and Development.Cell. No. 125, 30 June, pp. 1241-1252.Chang, D. and Clayton, D. (1985) Priming of human mitochondrial DNA replication occursat the light-strand promoter. Biochemistry. Vol. 82, January, pp. 351-355.Davidson, M. (2004) Mitochondria Internet, Florida State University. Available fromhttp//micro.magnet.fsu.edu/cells/mitochondria/mitochondria.htmlGray, M., Lang, B.F., Cedergren, R., Golding, G.B.,Lemieux, Sankoff, C.D., Turmel, M., Brossard, N., Delage, E.,Littlejohn, T.G., Plante, I., Rioux, P., Saint-Louis, D., Zhu, Y. andBurger, G . (1997) Genome structure and gene content in protest mitochondrial DNAs. Nucleic Acids Research. 26 (4), 1998, pp. 865-878.Ohta, N., Sato, N., and Kuroiwa, T. (1998) Structure and Organization fo the MitochondrialGenome of the Unicellular Red algae Cyanidioschyzon merolae Deduced from the Complete Nucleotide Sequence. Nucleic Acids Research. 26 (22), 24 September, pp. 5190-5198.Shadel, G. S., and D. A. Clayton. (1997) Mitochondrial DNA maintenance in vertebrates.Annu. Rev. Biochem. 66409435.Wallace, D.C. (2005). A mitochondrial paradigm of metabolic and degenerative diseases,aging, and cancer A dawn for evolutionary medicine. Annu Rev Genet. 39, pp. 359407