MARTIN ŠOLC CYIL 9 ȍ2018Ȏ from the nucleus, mitochondria are the only part of the human cell where DNA is located. However, while nuclear DNA contains approximately 20,000 protein-coding genes, 8,9 mtDNA only contains thirty sevens genes from which five are protein-coding. 10 The mtDNA only influences the function of mitochondria: 11 all other important human characteristics, be it the colour of eyes, intelligence, height, or any health issue unrelated to mitochondria, are determined by the nuclear DNA 12 . However, some mtDNA mutations can lead to rare but very serious health consequences including, for example, mitochondrial myopathies, encephalomyopathies, or complex multisystem syndromes. 13 A defect in mtDNA is the primary cause of these so-called mitochondrial diseases. 14 Causal treatments of these diseases are generally non-existent or only experimental. 15 MRT consists of several alternative procedures that take place in the context of in vitro fertilisation (IVF), i.e. the process of fertilisation in laboratory environment. It does not alter the nucleus of the fertilised egg, but it replaces the mitochondria carrying a harmful mutation with healthy mitochondria. 16 Technically, it is true that the resulting child carries DNA from 8 EZKURDIA, Iakes, JUAN, David, RODRIGUEZ, Jose Manuel, FRANKISH, Adam, DIERKHANS, Mark, HARROW Jennifer, VAZQUEZ, Jesus, VALENCIA, Alfonso, TRESS, Michael L. Multiple evidence strands suggest that there may be as few as 19,000 human protein-coding genes. Human Molecular Genetics. (2014, Vol. 23, No. 22), pp. 5866-5878. accessed 22 May 2018. 9 Genes fulfil their function when they are transcribed into RNA and this RNA is translated into proteins. See POLLARD, Thomas D., EARNSHAW, William C., LIPPINCOTT-SCHWARTZ, Jennifer. Cell Biology. 2 nd edition. Elsevier, New York 2008, p. 251. See also BRADLEY-SMITH, Guy, HOPE, Sally, FIRTH, Helen V., HURST, Jane A. Oxford Handbook of Genetics. Oxford University Press, Oxford 2010, p. 64. 10 See for example CHINNERY, Patrick Francis, HUDSON, Gavin. Mitochondrial genetics. British Medical Bulletin. (2013, Vol. 106, No. 1), p. 137. 11 See LODISH, Harvey, BERK, Arnold, KAISER, Chris A., KRIEGER, Monty, SCOTT, Matthew P., BRETSCHER, Anthony, PLOEGH, Hidde, MATSUDAIRA, Paul. Molecular Cell Biology . 6 th edition. W. H. Freeman and Company, New York 2008, p. 240. 12 See ibid., pp. 138-141. 13 See ZEVIANI, Massimo, DI DONATO, Stefano. Mitochondrial disorders. Brain: a Journal of Neurology. (2004, Vol. 127, No. 10), pp. 2153-2172. accessed 22 May 2018. For a more detailed overview see GVOZDJÁKOVÁ, Anna. Mitochondrial Medicine. In GVOZDJÁKOVÁ, Anna (eds.). Mitochondrial Medicine. Mitochondrial Metabolism, Diseases, Diagnosis and Therapy. Springer Science+Business Media B. V., Berlin 2008, pp. 103-113. 14 GVOZDJÁKOVÁ, Anna. Mitochondrial Medicine. In GVOZDJÁKOVÁ, Anna (eds.). Mitochondrial Medicine. Mitochondrial Metabolism, Diseases, Diagnosis and Therapy. Springer Science+Business Media B. V., Berlin 2008, p. 104. 15 For example, an experimental gene therapy was in the centre of the controversy surrounding the English infant Charlie Gard who was dying of a mitochondrial disorder, namely mitochondrial DNA depletion syndrome. See TRUOG, Robert D. The United Kingdom Sets Limits on Experimental Treatments. JAMA: The Journal of the American Medical Association. (2017, Vol. 318, No. 11), pp. 1001-1002, HOLČAPEK, Tomáš, ŠUSTEK, Petr, ŠOLC, Martin. Odpojení dítěte od přístrojů. Na okraj případu Charlie Gard. [The Withdrawal of Life-Sustaining Treatment in Children: A Note to the Case of Charlie Gard.] Právní rozhledy. (2018, Vol. 26, No. 3), pp. 94-103. 16 See The National Academies of Sciences, Engineering, and Medicine Committee on the ethical and social policy considerations of novel techniques for prevention of maternal transmission of mitochondrial DNA diseases. Mitochondrial replacement techniques: Ethical and social policy considerations. The National Academic Press, Washington, D.C. 2016, pp. 45-53. accessed 22 May 2018, CHINNERY, Patrick Francis, HUDSON, Gavin. Mitochondrial genetics. British Medical Bulletin. (2013, Vol. 106, No. 1), pp. 152-153. For a popularizing introduction to MRT see HESMAN SAEY, Tina. How to make a “three-parent” baby. Science News for Students. (21 February 2017.) accessed 22 May 2018.
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