Global challenges Study Guide

Infections are caused by pathogens, which are microorganisms that can cause disease. This topic requires you to understand the key characteristics of at least one common human infection, one plant disease, and sexually transmitted infections (STIs) in humans, including HIV/AIDS. For common human infections, measles is a good example. It's a viral disease spread by airborne droplets from coughs and sneezes. Symptoms include a red skin rash and fever. Measles can be serious, leading to pneumonia or encephalitis, and is largely prevented by the MMR vaccine. For plant diseases, tobacco mosaic virus (TMV) is a key example. This virus affects a wide range of plants, including tomatoes, peppers, and tobacco. It's spread by contact between plants and causes a distinctive mosaic pattern on leaves, stunting growth and reducing yields. There is no cure for TMV, so prevention involves good hygiene, removing infected plants, and using resistant varieties. Sexually transmitted infections (STIs) are passed from one person to another through sexual contact. HIV (Human Immunodeficiency Virus) is a prime example. HIV attacks the immune system, specifically white blood cells. Initial symptoms may be flu-like, but the virus can remain dormant for years. If left untreated, HIV progresses to AIDS (Acquired Immune Deficiency Syndrome), where the immune system is severely compromised, making the individual vulnerable to opportunistic infections and certain cancers. HIV is transmitted through the exchange of bodily fluids like blood, semen, vaginal fluids, and breast milk. Prevention methods include barrier contraception (like condoms), not sharing needles, and antiretroviral drugs to reduce viral load in infected individuals. This knowledge helps us understand how to prevent spread, identify symptoms, and manage these diseases.

The human genome is the complete set of genetic instructions in a human, stored as DNA. It contains all the information needed to build and maintain a human being. Our increasing understanding of the human genome, largely driven by the Human Genome Project, has opened up significant possibilities in medicine. This project successfully mapped the entire human genome, identifying all the genes within it. This knowledge allows scientists and doctors to pinpoint specific genes responsible for inherited diseases, such as cystic fibrosis, Huntington's disease, and sickle cell anaemia. By understanding the genetic basis of these conditions, it becomes possible to develop more accurate diagnostic tests, not only for individuals but also for prospective parents to assess risks for their children. Furthermore, this genetic insight paves the way for new therapeutic approaches, including gene therapy, where faulty genes are replaced or repaired. Pharmacogenomics, another emerging field, uses genomic information to predict how an individual will respond to different medications, leading to personalised treatment plans that are more effective and have fewer side effects. However, alongside these advancements, there are ethical considerations, including concerns about genetic discrimination and the privacy of genetic information. The cost of genomic sequencing and gene therapies can also be substantial, posing challenges for equitable access. Therefore, a balanced view recognises both the immense potential for improving health outcomes and the complex societal and ethical hurdles that must be addressed.