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In molecular biology, a stop codon is a codon that signals the termination of the translation process of the current protein. Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein; stop codons signal the termination of this process by binding release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain.
In biology, translation is the process in living cells in which proteins are produced using RNA molecules as templates. The generated protein is a sequence of amino acids. This sequence is determined by the sequence of nucleotides in the RNA. The nucleotides are considered three at a time. Each such triple results in addition of one specific amino acid to the protein being generated. The matching from nucleotide triple to amino acid is called the genetic code. The translation is performed by a large complex of functional RNA and proteins called ribosomes. The entire process is called gene expression.
In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid molecule into a set of consecutive, non-overlapping triplets. Where these triplets equate to amino acids or stop signals during translation, they are called codons.
Chargaff's rules state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further, a 1:1 stoichiometric ratio of purine and pyrimidine bases should exist. This pattern is found in both strands of the DNA. They were discovered by Austrian-born chemist Erwin Chargaff in the late 1940s.
A point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism's genome. Point mutations have a variety of effects on the downstream protein product—consequences that are moderately predictable based upon the specifics of the mutation. These consequences can range from no effect to deleterious effects, with regard to protein production, composition, and function.
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes.
Strongylocentrotus purpuratus is a species of sea urchin in the family Strongylocentrotidae commonly known as the purple sea urchin. It lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico, to British Columbia, Canada. This sea urchin species is deep purple in color, and lives in lower inter-tidal and nearshore sub-tidal communities. Its eggs are orange when secreted in water. January, February, and March function as the typical active reproductive months for the species. Sexual maturity is reached around two years. It normally grows to a diameter of about 10 cm (4 inches) and may live as long as 70 years.
MT-ND6 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 6 protein (ND6). The ND6 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Variations in the human MT-ND6 gene are associated with Leigh's syndrome, Leber's hereditary optic neuropathy (LHON) and dystonia.
MT-ND4 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 4 (ND4) protein. The ND4 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Variations in the MT-ND4 gene are associated with age-related macular degeneration (AMD), Leber's hereditary optic neuropathy (LHON), mesial temporal lobe epilepsy (MTLE) and cystic fibrosis.
MT-ATP6 is a mitochondrial gene with the full name 'mitochondrially encoded ATP synthase membrane subunit 6' that encodes the ATP synthase Fo subunit 6. This subunit belongs to the Fo complex of the large, transmembrane F-type ATP synthase. This enzyme, which is also known as complex V, is responsible for the final step of oxidative phosphorylation in the electron transport chain. Specifically, one segment of ATP synthase allows positively charged ions, called protons, to flow across a specialized membrane inside mitochondria. Another segment of the enzyme uses the energy created by this proton flow to convert a molecule called adenosine diphosphate (ADP) to ATP. Mutations in the MT-ATP6 gene have been found in approximately 10 to 20 percent of people with Leigh syndrome.
Mitochondrially encoded tRNA leucine 1 (UUA/G) also known as MT-TL1 is a transfer RNA which in humans is encoded by the mitochondrial MT-TL1 gene.
Lipoamide acyltransferase component of branched-chain alpha-keto acid dehydrogenase complex, mitochondrial is an enzyme that in humans is encoded by the DBT gene.
Mitochondrially encoded tRNA isoleucine also known as MT-TI is a transfer RNA which in humans is encoded by the mitochondrial MT-TI gene.
ADP/ATP translocase 3, also known as solute carrier family 25 member 6, is a protein that in humans is encoded by the SLC25A6 gene.
Numerous key discoveries in biology have emerged from studies of RNA, including seminal work in the fields of biochemistry, genetics, microbiology, molecular biology, molecular evolution, and structural biology. As of 2010, 30 scientists have been awarded Nobel Prizes for experimental work that includes studies of RNA. Specific discoveries of high biological significance are discussed in this article.
ADP/ATP translocase 2 is a protein that in humans is encoded by the SLC25A5 gene on the X chromosome.
The vertebrate mitochondrial code is the genetic code found in the mitochondria of all vertebrata.
The invertebrate mitochondrial code is a genetic code used by the mitochondrial genome of invertebrates. Mitochondria contain their own DNA and reproduce independently from their host cell. Variation in translation of the mitochondrial genetic code occurs when DNA codons result in non-standard amino acids has been identified in invertebrates, most notably arthropods. This variation has been helpful as a tool to improve upon the phylogenetic tree of invertebrates, like flatworms.
The alternative flatworm mitochondrial code is a genetic code found in the mitochondria of Platyhelminthes and Nematodes.
References
This article incorporates text from the United States National Library of Medicine, which is in the public domain. [1]
- 1 2 Elzanowski A, Ostell J, Leipe D, Soussov V. "The Genetic Codes". Taxonomy browser. National Center for Biotechnology Information (NCBI), U.S. National Library of Medicine. Retrieved 18 March 2016.
- ↑ H. Himeno; H. Masaki; T. Kawai; T. Ohta; I. Kumagai; K. Miura; K. Watanabe (1987). "Unusual genetic codes and a novel gene structure for tRNA(AGYSer) in starfish mitochondrial DNA". Gene. 56 (2–3): 219–30. doi:10.1016/0378-1119(87)90139-9. PMID 3678836.
- ↑ H. T. Jacobs; D. J. Elliott; V. B. Math; A. Farquharson (20 July 1988). "Nucleotide sequence and gene organization of sea urchin mitochondrial DNA". J Mol Biol. 202 (2): 185–217. doi:10.1016/0022-2836(88)90452-4. PMID 3172215.
- ↑ P. Cantatore; M. Roberti; G. Rainaldi; M. N. Gadaleta; C. Saccone (5 July 1989). "The complete nucleotide sequence, gene organization, and genetic code of the mitochondrial genome of Paracentrotus lividus". J Biol Chem. 264 (19): 10965–75. doi: 10.1016/S0021-9258(18)60413-2 . PMID 2544576.
- ↑ M. J. Telford; E. A. Herniou; R. B. Russell; D. T. Littlewood (10 October 2000). "Changes in mitochondrial genetic codes as phylogenetic characters: two examples from the flatworms". Proc Natl Acad Sci U S A. 97 (21): 11359–64. Bibcode:2000PNAS...9711359T. doi: 10.1073/pnas.97.21.11359 . PMC 17205 . PMID 11027335.
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