In 1970 Francis Crick published an article in the scientific journal Nature on the central dogma of molecular biology, presenting the normal flow of genetic information, as shown in Figure 1 (Crick, 1970). Although many discoveries have been made since then, the main idea is still valid: each organism uses its own DNA sequence to synthesize its own proteins (Crick, 1970). To function properly, the genome must be kept intact, any damage can potentially affect the structure of a protein, interfering with its function (Brown, 2010). Although evolution has equipped every functional cell with a molecular toolkit designed to repair and thus prevent DNA damage, errors still occur. Those errors that remain buried in the genome of a cell and are sometimes passed on to the next generation are called DNA mutations. Because DNA codes for proteins and RNA molecules, almost any change in the DNA sequence, if left unrepaired, can cause physiological malfunctions, known as genetic diseases. According to the Global Genes Project, there are more than 7,000 rare genetic diseases. Despite these alarming data, genetic diseases are not rare since DNA is a rather fragile molecule and prone to damage. Many types of mutations have been analyzed and classified, the simplest of which is the point mutation. Changing one base pair to another has been linked to life-threatening diseases such as sickle cell anemia. In sickle cell anemia, the structure of the β-strand of the hemoglobin protein has been modified by the substitution of glutamic acid (Ingram, 1957). At the molecular level, the change from glutamic to valine corresponds to a change of adenine to thymine (Marotta et al., 1977), leaving the peptide chain with a loss of negative...... middle of paper.... ..and mitochondria and a possible contribution to mutagenesis through reduced replication fidelity. Proceedings of the National Academy of Sciences 102, 4990-499522. Taylor, RW and Turnbull, DM (2005) Mitochondrial DNA mutations in human disease. Nature Examines Genetics 6, 389-40223. Thibodeau PH, et al., (2010). The deltaF508 mutation causing cystic fibrosis affects multiple steps in the biogenesis of the cystic fibrosis transmembrane conductance regulator. J. Biol. Chem.285, 35825–3583524. Transtutors.com. 2014. Genetic Anomalies and Disorders Help for Chromosomes - Transtutors. [online] Available at: http://www.transtutors.com/homework-help/biology/chromosomes-genetic-disorder/gene-abnormalities-and-disorders.aspx [Accessed: 21 March 2014].25. Viguera, E., et al. Replication slippage involves pausing and dissociation of DNA polymerase. EMBO Journal 20, 2587–2595 (2001)