EMA Medical Terms Simplifier
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EXPLAINER
What are genes?
Our genes determine our makeup and we inherit them from our parents. A gene is a set of precise
instructions for making a specific protein in a cell. We have a bank of between 20,000 and 25,000 different
genes. Each gene forms a small section of the long strands of DNA (chromosomes), present in the nucleus of
the cell.
Cells make copies of the DNA when they divide. The copies can develop mistakes but these are usually
repaired and there is no effect on the genes. For many of the remaining mistakes, the consequences are
minor and go unnoticed. But, rarely, mistakes lead to an alteration (mutation) of a gene and affect the
production of an important protein and so cause disease. Cystic fibrosis, a disease affecting the lungs and the
digestive system, is an example of a disease caused by faulty genes.
Genetic diseases are challenging to treat. Treatment focuses on relieving symptoms of the disease and,
where possible, replacing the missing or abnormal protein resulting from the faulty gene. For some diseases,
advanced medicines may be able to introduce genes into body cells and so correct the underlying genetic
abnormality, possibly permanently.
genotoxic substance a substance that is harmful to the DNA, the genetic material in cells
glaucoma damage to the nerve in the eye <usually caused by high pressure in the eye>
glaucoma, angle-
closure
damage to the nerve in the eye caused by pressure inside the eye rising rapidly
because fluid cannot drain out
glaucoma, narrow-
angle
see glaucoma, angle-closure
glaucoma, open-angle
damage to the nerves in the eye caused by high pressure due to clogging of fluid
drainage canals
glioma
a type of brain tumour that begins in ‘glial’ cells (the cells that surround and
support nerve cells)
glossodynia burning or tingling sensation in or around the mouth