April 25th: World DNA Day
The discovery of DNA is one of the most significant milestones in the history of science and, to this day, remains the basis for many medical discoveries and advances. April 25th is the day on which two main passages in genetics and, by extension, in science, in general, are commemorated:
- the discovery of the structure of the DNA double helix in 1953
- the completion of the Human Genome Project in 2003, 50 years later.
Therefore, this date has become a day to commemorate these two milestones, but DNA Day is also a day to broaden knowledge.
The double helix
The DNA structure was published in the Nature magazine under James Watson y Francis Crick name, both of whom, together with Maurice Wilkins, won the Nobel Prize for their investigation labor, in the year 1962.
The great overlooked in this story was Rosalind Franklin, the author of the X ray images that were critical to achieve this important scientific milestone. You can watch this documentary if you want to know a bit more about Rosalind Franklin.
The double helix is the concept used to describe the structure of a molecule of DNA, which it is conformed by two strands, that intertwine themselves in an helicoidal manner. Each strand has a backbone of carbohydrate and phosphate groups. Linked to each carbohydrate there is one of 4 bases: adenine (A), cytosine (C), guanine (G), or thymine (T). Both strands maintain their link due to the bonds formed in between the following base pairs: adenine bonds with thymine; and cytosine, with guanine.
This discovery forever changed our understanding of genetics and the study of how the physiological and physic inheritance is transmitted from one generation to another.
The Human Genome Project
Over the decades, more and more DNA-related discoveries have been made, which led to a deeper understanding of DNA. Still, the complete genome remained a challenge until, in 2003, scientists completed a project to map the entire human DNA. More than 20,000 genes were identified, and the sequence of three trillion base pairs that comprise the human genome was determined.
Francis Collins, the director of the National Human Genome Research Institute, stated that the genome is like a book with multiple uses: it’s valid as a narrative of the journey of the human species over time, as an incredibly detailed blueprint for constructing each cell of the organism and, of course, as a tool that provides health professionals with new ways to treat and, above all, prevent disease.
However, although the human genome project was completed in 2003, it’s actually at the end of March 2022 when the 100% complete human genome, including repetitive DNA, will be published for the first time.
The most common form of repetitive DNA is tandemly repeating blocks of DNA called satellites. These are clustered at the ends of chromosomes in regions known as telomeres, which protect chromosomes from degradation during DNA replication.
This is a new scientific milestone, as the gaps left in 2003 have finally been filled. Find out more about the Human Genome Project.
The human genome and health
The Human Genome Project has been fundamental to understanding human genetics, leading to numerous advances in various areas of health.
Some of the areas in which the project has had a significant impact include:
- Diagnosis and treatment of genetic diseases.
- Personalized medicine. For example, genome information can be used to select the most effective drug for a specific patient and avoid medications that could have dangerous side effects (pharmacogenetics).
- Complex disease research. Genetic variants associated with complex diseases (those caused by the interaction of multiple gene variants and environmental factors) have been identified, leading to a better understanding of the underlying biology of these diseases and the identification of new therapeutic targets.
- Development of gene therapies. Information from the human genome has been essential in developing gene therapies, which involve correcting or eliminating defective genes to treat genetic diseases.
We will further develop the diagnosis of genetic diseases with an example: cystic fibrosis. Cystic fibrosis is a genetic disease that mainly affects the lungs and digestive system and is caused by mutations in the CFTR gene (Cystic Fibrosis Transmembrane Conductance Regulator). It’s a genetic disease with an autosomal recessive inheritance: for a person to have the disease, they must have inherited two copies of the mutated CFTR gene (one from each of their parents).
The CFTR gene was described as the cause of cystic fibrosis in the 1980s. This gene codes for a homonymous protein found in cell membranes with exocrine function, meaning it synthesizes substances released into or onto the surface of other body organs. The CFTR protein facilitates the transport of chloride ions from the inside to the outside of the cell actively across the cell membrane. In patients with cystic fibrosis, the CFTR protein doesn’t function properly, resulting in a buildup of thick, sticky mucus in the lungs and other organs, which makes breathing difficult. In addition, it makes people with the disease more susceptible to respiratory infections. The mucus buildup can also block the pancreatic ducts, which prevents the pancreas from producing enough digestive enzymes to break down food. This can lead to digestion problems and improper absorption of nutrients.
Cystic fibrosis is a chronic, progressive disease whose symptoms vary from person to person. However, the most common symptoms include chronic cough, shortness of breath, recurrent lung infections, difficulty gaining weight, digestive problems, and growth retardation.
Although there isn’t a cure for this disease, there are treatments that can help control symptoms and improve the quality of life for those affected. Treatments may include medications to help lighten mucus in the lungs, respiratory therapy, nutritional supplements, and other therapies to treat digestive problems. Research continues progressing, and new therapies and treatments are expected to be developed.
Thanks to the knowledge gained from the Human Genome Project and the rise of sequencing techniques, learning about this disease has increased enormously in recent years. More than 2,000 mutations in the CFTR gene that can lead to cystic fibrosis are known. Some modifications are more common in certain ethnic groups, and the severity of the disease can vary depending on the type of mutation.
Diagnosis of cystic fibrosis is based on genetic testing to identify mutations in the CFTR gene. These tests can be performed in people who present symptoms of the disease and in people who are carriers of a CFTR gene mutation and who can pass it on to their children.
24Genetics’ main goal is to help people by providing them with personalized, science-based genetic information, to make the best decisions for their health and well-being.
Seeing one’s genetic predisposition to a specific disease allows us to take preventive action and special care. From this principle arises precision medicine, which you can learn more about in this post on our blog.
Bibliography
[1] Christodoulou J. (2003). The human genome project: opportunities, challenges and consequences for population screening. The Southeast Asian journal of tropical medicine and public health, 34 Suppl 3, 234-238.
[2] Deoxyribonucleic Acid (DNA) (n.d.). Retrieved April 17, 2023, from https://www.genome.gov/genetics-glossary/Deoxyribonucleic-Acid
[3] Rosalind Franklin was so much more than the ‘wronged heroine’ of DNA. (2020). Nature, 583(7817), 492. https://doi.org/10.1038/d41586-020-02144-4. https://doi.org/10.1038/d41586-020-02144-4
[4] Moreno-Palanques R. (1995). The human genome project and its applications [El proyecto del genoma humano y sus aplicaciones]. University of Navarra Journal of Medicine, 40(2), 64-67.
[5] O’Sullivan, B. P., & Freedman, S. D. (2009). Cystic fibrosis. Lancet (London, England), 373(9678), 1891-1904. https://doi.org/10.1016/S0140-6736(09)60327-5.
[6] Welsh, M. J., & Smith, A. E. (1993). Molecular mechanisms of CFTR chloride channel dysfunction in cystic fibrosis. Cell, 73(7), 1251-1254. https://doi.org/10.1016/0092-8674(93)90353-r
[7] Katz, J. B., Shah, P., Trillo, C. A., Alshaer, M. H., Peloquin, C., & Lascano, J. (2023). Therapeutic drug monitoring in cystic fibrosis and associations with pulmonary exacerbations and lung function. Respiratory medicine, 212, 107237. Advance online publication. https://doi.org/10.1016/j.rmed.2023.107237
