Key Terms You Must Know

📖 Key Terms You Must Know

DNA (deoxyribonucleic acid)

The molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms. Its double helix structure was discovered by James Watson and Francis Crick in 1953 (building on X-ray crystallography work by Rosalind Franklin). The discovery established that hereditary information was encoded chemically and could be read, copied, and theoretically edited — opening the fields of genetic medicine, genetic testing, and gene therapy. For AQA, DNA is the 20th century's equivalent of germ theory in terms of its transformative impact on medicine's direction.

Antibiotic resistance

The ability of bacteria to survive exposure to antibiotics that previously killed them, acquired through evolutionary mutation and natural selection. Caused primarily by the overuse of antibiotics (prescribing for viral infections they cannot treat; agricultural use in livestock). Leading resistant organisms include MRSA (Methicillin-resistant Staphylococcus aureus) and C. difficile. Resistance is a major modern healthcare challenge because it threatens to make routine infections — previously easily treated — untreatable. The WHO estimates antimicrobial resistance could cause 10 million deaths annually by 2050. It is the most significant long-term threat to the gains made by penicillin and subsequent antibiotics since 1944.

Human Genome Project

An international scientific project completed in 2003 that mapped all 20,000+ human genes — the complete DNA sequence of the human genome. Involving scientists from six countries (USA, UK, France, Germany, Japan, China), it took 13 years and cost approximately $3 billion. Its significance: it established the genetic basis of thousands of diseases, enabling genetic screening and diagnosis; it opened the possibility of personalised medicine (treatments tailored to individual genetic profiles); and it provided the foundation for gene therapy and CRISPR gene editing. The project is an example of the "technology" and "government/international collaboration" factors in modern medicine.

Transplant surgery

The surgical procedure of replacing a failed or damaged organ with a functioning one from a donor. Joseph Murray performed the first successful kidney transplant in 1954 (between identical twins). Christiaan Barnard performed the first human heart transplant in 1967 in South Africa — the patient lived 18 days. Heart, liver, lung, and kidney transplants are now routine in modern hospitals, saving thousands of lives annually. Key enabling factors: improved surgical technique, discovery of immunosuppressant drugs (to prevent organ rejection), and better organ preservation and matching technology.

Lifestyle diseases

Illnesses caused or significantly worsened by lifestyle choices — primarily diet, physical activity, smoking, and alcohol consumption. Examples: type 2 diabetes (often linked to obesity), heart disease (linked to diet, smoking, and inactivity), lung cancer (strongly linked to smoking), liver disease (linked to alcohol). These now account for the majority of deaths and NHS costs in the UK. Unlike infectious diseases (where medicine can cure or prevent), lifestyle diseases require behaviour change that medicine alone cannot deliver. They represent a fundamentally different challenge to the healthcare system than the bacterial infections that dominated medicine in the 19th and early 20th centuries.

Gene therapy

An experimental medical technique that treats or prevents disease by correcting faulty genes or inserting functional genes into a patient's cells. Based on Watson and Crick's 1953 discovery of DNA structure and subsequent mapping of the human genome. Early clinical trials for sickle cell disease using gene therapy began showing success from 2019 onwards, with patients achieving sustained remission. CRISPR-Cas9 (2012) is the current cutting-edge gene editing technology, capable of precisely cutting and modifying DNA sequences. Gene therapy represents the potential future of personalised medicine — treating disease at its molecular root cause rather than managing symptoms.