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Glossary

Amino acid - The “building blocks” of proteins.  The sequence of amino acids determines the shape, properties and role of the protein.

Amniocentesis - Removal of a sample of amniotic fluid for prenatal testing.  Cells from the unborn child can be extracted from the fluid which surrounds it in the womb, and tested for certain abnormalities.

Anaesthetic – an agent that reduces or stops sensation.  It can either be general (whole body) or local (affecting a particular part of the body).

Atrophy – wasting away.  Usually refers to the muscles.

Autosomal inheritance – Autosomes are the chromosomes other than the X and Y chromosomes (the sex chromosomes).  Autsomal inheritance means that the abnormal gene can affect either sex.  It can be dominant or recessive.

Axon – An extension of a neuron that carries the signal to target cells.

Biopsy – Removal of a small amount of tissue for examination.

Carrier – An individual who has one normal gene and one abnormal copy of a pair of a gene for a genetic disorder.  A carrier of a gene for a recessive disorder will usually remain unaffected throughout life.  A carrier can pass the faulty gene on to their offspring.

Carrier testing – Genetic testing to find out if a person who does not show symptoms of a condition nevertheless “carries” a copy of a faulty gene which could be passed on to his or her children.

Cell – The Basic structural unit of all living organisms.  The cell is surrounded by a membrane.  Inside the cell is a structure called the nucleus.  The nucleus contains DNA, arranged into chromosomes which carry the genes that we inherit.

Central nervous system (CNS) – The brain and spinal cord.

Chiropodist – a foot care specialist. (see also Podiatrist). 

Chorionic villus sampling (also known as CVS) – Removal of chorionic villi for prenatal testing.  The chorionic villi are cells situated on the wall of the uterus (womb) which form the early placenta (afterbirth).  They have the same genetic make-up as the unborn baby, and can be tested to detect certain abnormalities.

Chromosomes – Cylindrical-shaped bundles in the cell nucleus, made of a very long thin strand of the chemical molecule DNA, coiled upon itself many times.  Humans have 46 chromosomes (23 pairs) in most cells of their bodies.  The sex cells (the unfertilised egg and sperm) contain only 23 unpaired chromosomes each.  Fertilisation of a 23-chromosome egg by a 23-chromosome sperm produces a new 46-chromosome cell, which grows into a new individual.  In this way, one of each chromosome pair is inherited from each parent.  The genes we inherit are located on the chromosomes.

Congenital – Present at birth, or soon afterwards.

Contractures – Shortening of muscles or tendons, which prevents the associated joints from moving freely.

Deletion – The loss of a bit of genetic material from a chromosome or gene.

Distal – Away from the centre of the body.

DNA – Deoxyribonucleic acid, the chemical composition of genes.  It contains coded information arranged in a linear sequence.  Each cell’s chromosomes contain about two metres of DNA, yet it is so thin that it is barely visible even with the most powerful microscope.  If all the DNA in a human body were stretched end to end it would be long enough to reach the moon and back about 10,000 times.

Dominant – In dominant inheritance, if one of a pair of genes is altered, the individual possessing that gene will show signs of the relevant disorder.  In any pregnancy, there is a 50% chance that he or she will pass the altered gene on, giving rise to a child who is also affected.

Duplication – Where a part of a chromosome or gene is repeated.

Genes – The coded instructions that govern the make-up of every human being.  Genes are made of DNA.  Each gene carries instructions for the production of a specific protein.  Genes usually come in pairs, one inherited from each parent.  They are passed on from one generation to the next, and are the basic units of inheritance.  Alterations in genes (mutations) can cause inherited disorders.

Genetic counselling – Information and supported provided by a specialist, usually a doctor or nurse, to people who have genetic conditions in their families, or who are concerned of the possibility of genetically transmitted conditions.

Genetic disorders – Conditions that result from alterations in the genetic make-up of an individual.  They may be the consequence of defects in single genes, or in whole chromosomes, parts of which may be lost, duplicated, misplaced or replaced; or may result from the interaction of multiple genes and external factors such as the environment.

Genetic testing – Examination of an individual’s genetic material to identify faults that may cause a disorder.

Genome – The complete set of genes of a person or organism.

GP – general practioner.  A doctor who is a general health specialist.  They are the gateway to most other health and social services.

Inheritance – The acquisition of characteristics from a parent or ancestor.

Linkage studies – These are tests carried out on various family members to establish how a particular piece of genetic information runs through a family.  It can sometimes be used to predict whether an individual has inherited a faulty gene.

Manifesting carrier – A female carrier of an X-linked condition who exhibits symptoms.

Membrane – Membranes form a barrier between the inside and outside of a cell.  Membranes protect cells and control which substances leave or enter a cell.

Mutation – When a gene is changed or altered in some way.  Mutations can be passed onto subsequent generations.

Myelin – Insulating material which surrounds nerves and causes nerve impulses to be conducted faster.

Nerves – bundles  of axons that transmit signals around the body.

Neuron – Cells that produce signals, in the form of electrical impulses, which travel via the axons.

Neurologist – specialist in nervous system disorders.

Neurology – any disease of the nervous system.

Neuropathy – any disease of the peripheral nervous system.

Occupational Therapist (OT) – Independent living specialist.

Orthopaedic – To do with bones.

Orthosis – A mechanical device which provides very specific support to your joints and limbs.

Orthotics – the assessment of patients using biomechanical principles to design, provide and monitor the ongoing use of orthoses.

Osteotomy – cutting the bone and repositioning it.

Paediatrician – child health doctor.

Peripheral Myelin Protein 22 (PMP22) – Both increased and decreased levels of this protein are associated with some forms of CMT.

Peripheral nervous system – The nervous system which links the spine and brain to the skin, muscles, blood vessels and other sensory organs.

Pes cavus – medical name for a highly arched foot.

Physiotherapist (physio) – movement specialist.

Podiatrist – a foot care specialist. (see also Chiropodist).

Prenatal – Literally, before birth.

Prognosis – Predicted course and outcome of a disorder.

Progressive – When talking about a disease, is the term used to explain that the condition gets worse (cannot be stopped).

Protein – One or a few long chains of amino acids linked in sequence.

Proximal – Close to the centre of the body.

Recessive – A form of inheritance where a faulty copy of a gene is inherited from each parent ie, in order to develop the disorder an individual has to have two copies of the faulty gene.  Includes X-linked recessive and Autosomal recessive modes of inheritance.

Scoliosis – Curvature of the spine.

Sex chromosomes – The X and Y chromosomes determine the sex of an individual.  Females have two X chromosomes; males have an X and a Y chromosome.

Tendon transfers – Moving a working tendon and muscle group and attaching the end of the tendon to a new place so that it works in a different manner.  Often the tendon/muscle causing the deformity is moved to work in the opposite direction to prevent the chance of deformity occurring again.

Tissue – A group of cells organised to carry out a particular job or function.

Trial – An experimental run, eg. a test of a certain therapy on animals or humans.

Triple arthodesis – stabilizing of a joint by fusing (welding) three bones together (arthrodesis is another term for fusing).

Varus heel – the characteristic curved in shape of the heel on a person affected by CMT.

X-linked – A form of inheritance where the gene in question lies on the X chromosome.  X-linked genes can be dominant, but are usually recessive.  Girls who carry an altered gene are usually not affected, since they have a second, normal copy of the gene, but they are carriers and can pass the affected gene on in 50% of their pregnancies.  Boys, who only have one X chromosome, do not have the second normal copy of the gene, so they will be affected by the disorder in question.  They will pass on the altered gene to all of their daughters, who will be carriers, but to none of their sons