In the nucleus of each eukaryotic cell, the DNA is packaged together into chromosomes. Each chromosome is made up of DNA that is tightly coiled around proteins that give it the structure. Chromosomes usually occur in pairs, except for gametes (eggs and sperm cells) but the number of chromosomes
A pathogen is a microorganism that can cause disease. Pathogens may be viruses, bacteria, protists or fungi. Examples of bacteria infections are cholera, typhoid, food poisoning and gonorrhoea. Examples of viral infections are the flu (influenza), measles, mumps, the common cold and AIDS. Some com
Vaccinations protect both humans and animals from a wide range of preventable and potentially serious illnesses. With vaccines, we take advantage of one of the most important aspects of the immune system: the ability to develop immunological memory. This means that once a person or animal is expose
