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Amniocentesis:
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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.
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Autosomes:
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All the chromosomes other than the X and Y (the sex chromosomes) are known as autosomes. Autosomal inheritance means that an abnormal gene can affect either sex.
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Cell:
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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.
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Cell Therapy:
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See Myoblast transfer
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Chorionic villus sampling (also known as CVS):
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Removal of chorionic villi for prenatal testing. The chorionic villa 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.
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Chromosomes:
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Sausage 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 unfertilized egg and sperm) contain only 23 unpaired chromosomes each. Fertilization 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 half of each chromosome pair is inherited from each parent.
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Congenital:
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Present at birth or soon afterwards.
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Contractures:
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Shortening of muscles or tendons which prevents the associated joints from moving freely
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Deletion:
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The loss of a bit of genetic material from a chromosome or gene.
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DNA - Deoxyribonucleic Acid:
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The chemical of which genes are made. 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.
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Dominant:
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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 percent chance that he or she will pass the altered gene on giving rise to a child who is also affected.
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Duplication:
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Where a part of a chromosome or gene is duplicated.
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Enzyme:
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A protein that triggers chemical reactions.
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Gene therapy:
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A potential method of treatment for genetic disorders which involves making correct copies of the gene in question and then transporting them into the cells of the body.
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Genes:
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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) which lead to abnormal function of the corresponding protein can cause inherited disorders.
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Genetic counseling:
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information and support provided by a specialist usually a doctor or nurse to people who have genetic conditions in their families or who are concerned about the future possibility of genetically transmuted conditions.
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Genetic disorders:
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Conditions which result from alterations in the genetic make-up of an individual. They may be the consequences of defects in single genes or in whole chromosomes parts of which may be lost, duplicated or misplaced: or may result from the interaction of multiple genes and external factors.
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Genetic markers:
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Harmless variations in the DNA which lie close to the site of a disrupted gene which may be used for tracking the condition through a family.
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Linkage studies:
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These are tests carried out on various family members to establish which is the crucial bit of genetic code causing a particular condition in that family.
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Immune response:
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The response by the body to "foreign" material (transplant or infection).
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Manifesting carrier:
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A female carrier of an X-linked condition who shows symptoms.
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Muscle fibre:
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The basic unit of muscle tissue formed by the fusion of groups of muscle cells.
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Mutation:
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When a gene is changed or altered in some way this is called a mutation. Mutations can be passed on to subsequent generations.
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Myoblast transfer:
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A potential method of treatment for Duchenne muscular dystrophy which involves the transplantation of billions of healthy donor cells into muscle. This is sometimes known as cell therapy.
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Nucleus:
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Structure in the centre of each cell which contains the chromosomes with their genetic material.
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Orthoses:
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Devices or aids to prevent, correct or control deformities.
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Preclinical diagnosis:
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Diagnosis of a genetic disorder before there are any symptoms of that disorder.
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Prenatal:
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Literally, before birth.
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Prognosis:
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Predicted course and outcome of a disorder.
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Recessive:
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A form of inheritance where a genetic defect causes little or no outward effect unless it is present in both of a pair of genes and has therefore been inherited from both parents. If a person has inherited one altered gene and one normal gene he or she will not be affected but will be a gene carrier. If two carriers of the same altered gene have children in each pregnancy there is a 25 percent chance that the child will inherit two copies of the altered gene and will be affected.
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Sex chromosomes:
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The X and Y chromosomes determine the sex of an individual. Females have two X chromosomes: males have an X and a Y chromosome.
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Ultrasound:
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This is a technique which uses reflected sound waves to see a hidden object. it is now widely used in medicine for example to obtain images of muscle structure and internal organs or of the unborn child.
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X-linked:
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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 can pass the affected gene on in 50 percent of their pregnancies. Boys who have only one X chromosome do not have a 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.
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Fact Sheets