Malaria – a growing threat
Glossary
allele. Genes can exist in more than one form. Each different form of the same gene is called an allele. For example, in the case of seed shape, there is one allele that determines wrinkled seeds and another allele that determines round seeds.
antibody. A protein produced by the body's immune system in response to a foreign substance (antigen). An antibody reacts specifically with the antigen that induced its formation and inactivates the antigen. Our bodies fight off an infection by producing antibodies.
antigen. Any foreign substance, usually a protein, that stimulates the body's immune system to produce antibodies. (The name antigen reflects its role in stimulating an immune response – antibody generating.)
B-cell (B-lymphocyte). A type of white blood cell that originates and develops in the bone marrow. B-cells can be stimulated to produce antibodies.
cerebral malaria. A type of malaria in which the red blood cells obstruct the blood vessels in the brain. Other vital organs can also be damaged. Cerebral malaria often leads to the death of the patient.
gamete. A cell, such as a sperm or an egg, that is specialised for fertilisation. Gametes have a single set of chromosomes.
gametocyte. A cell that can develop into a gamete.
gene. The basic unit of inheritance. A gene is a segment of DNA that specifies the structure of a protein or an RNA molecule.
genetic diversity. The variety of different types of genes in a species or population. Genetic diversity is really a form of biodiversity.
immune system. The cells, tissues and organs that assist the body to resist infection and disease by producing antibodies and/or altered cells that inhibit the multiplication of the infectious agent.
meiosis. A division of the nucleus that involves the separation of pairs of chromosomes into different cells. Meiosis takes place in the reproductive organs of sexually reproducing organisms. Meiosis involves two nuclear divisions, both of which may take place before division of the cell itself is complete. The eventual result is four cells, each with half the number of chromosomes present in the original cell. Crossing over of chromosomes during meiosis creates new combinations of genes in the progeny that were not present in either adult. For more information see How cells divide: Mitosis versus meiosis (Public Broadcasting Service, USA).
merozoite. A cell formed by asexual reproduction in the life cycle of plasmodium. Merozoites disperse and infect additional red blood cells within the host.
parasitaemia. The presence of parasites in the blood.
parasite. An organism that lives on or in an organism of a different species (the host) and gains some advantage at the host's expense.
pathogen. An organism capable of causing a disease.
phagocyte. A type of white blood cell that can engulf and destroy foreign organisms, cells and particles. Phagocytes are an important part of the immune system.
polymorphic. Literally meaning having more than one form. In terms of genes it means that there are several variants (alleles) of a particular gene that occur simultaneously in a population.
protozoan. A single-celled animal.
quinine. A bitter-tasting drug obtained from the bark of the cinchona tree. This plant is related to coffee and gardenia. Quinine has been used in the treatment of malaria.
sporozoite. One stage of the Plasmodium life cycle. Sporozoites are formed in the mosquito and are transferred to the host where they move to the liver cells.
vaccine. A preparation consisting of antigens of a disease-causing organism which, when introduced into the body, stimulates the production of specific antibodies or altered cells. This produces an immunity to the disease-causing organism. The antigen in the preparation can be whole disease-causing organisms (killed or weakened) or parts of these organisms.
Posted June 1997.