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Alleles
Different forms of a gene found at a particular position on a chromosome.
Amino acids
These are the building blocks which are used to make proteins. The genetic information found in DNA controls the formation of amino acid sequences which are used to make different proteins. There are 20 different sequences of amino acids.
Anti-oncogene
Also known as a tumour suppressor gene. This is a gene that helps stop cancer cells developing from normal cells, by inhibiting cell division. Thus, most tumour suppressor genes act as part of a quality control mechanism, by use of protein products to stop faulty cells from dividing and perpetuating their faults. In a cell, if both copies of a tumour suppressor gene are damaged (mutated), cancer may develop.
Antigen
A molecule which may stimulate an immune response.
Apoptosis
Programmed cell death.
Autosomal dominant inheritance
A single abnormal gene on one of the autosomal chromosomes from either parent can cause the disease. One of the parents will have the disease (since it is dominant) in this mode of inheritance; that person is called the carrier. Only one parent must be a carrier in order for the child to inherit the disease. See dominant.
Autosomal recessive inheritance
An abnormal gene on one of the autosomal chromosomes from each parent is required to cause the disease. People with only one abnormal gene in the gene pair are carriers, but since the gene is recessive they do not exhibit the disease. Both parents must be carriers in order for a child to have symptoms of the disease; a child who inherits the gene from one parent will be a carrier. See recessive.
Autosome
A chromosome that is not one of the sex chromosomes. Humans have 22 pairs of autosomes and a pair of sex chromosomes, one of each pair inherited from the mother and one from the father. There are 2 copies of each autosomal gene, one on each chromosome.
Base Pairs
Chemicals that pair to form DNA. Adenine (A) pairs with thymine (T); cytosine (C) pairs with guanine (G).
Benign
A confined growth/tumour which is not malignant. Tumours that are benign have a lower rate of cell division then malignant tumours.
Cancer
Invasive unregulated cell growth that is capable of spreading elsewhere.
Carcinogen
An agent that is capable of causing cancer.
Carcinoma in situ
Cancer at an early stage, where its surroundings have not been invaded.
Carrier
An individual who has a faulty (mutated) gene and one normal gene for a genetic disorder or a characteristic.
Cell
The basic unit of structure of all living organisms. In the nucleus of the cell are found the chromosomes which contain DNA, the genetic material of inheritance. Different sequences of DNA are known as genes.
Cell cycle
The sequence of phases through which a dividing cell must pass in order to multiply. During the cell cycle, quality control mechanisms ensure that faulty cells correct their defects or self-destruct.
Chromosome
A structure found in the cell nucleus which contains genetic material (DNA). Humans have 23 pairs of chromosomes, one of each pair is inherited from the mother and one from the father. Each chromosome contains many hundreds or thousands of genes which make up our genetic blueprint.
Clone
A single cell that can produce identical cells.
Clinical geneticist
Doctor who specialises in the assessment and management of patients who may have, or be at risk of a genetic disease.
Colonoscopy
An investigation to examine the lining of the colon (large bowel) by using a long, narrow flexible tube which is inserted into the anus.
DNA (deoxyribonucleic acid)
The substance that contains genetic material, found in chromosomes in the cell nucleus. The genetic instructions contained in DNA are needed to build a living being and for the day to day activities of each body cell, such as growth, development and replication.
DNA repair gene
The are several genes which control DNA proof - reading and repair. These mechanisms are essential in order to ensure that the genome remains as fault-free as possible.
Dominant
A characteristic that is apparent when there is only one copy of the particular gene is present, or in the case of a genetic disease when only one copy is abnormal.
FAP
Familial Adenomatous Polyposis. A condition where a large number of polyps (over 100) develop in the bowel. The development of bowel cancer from the age of 20 onwards is a near certainty if the condition is left untreated.
Familial cluster
A pattern of similar cancers in a family. The term may be used in relation to families who do not fit standard referral criteria.
Family cancer/history clinic
A clinic at which an individual with a family history of cancer is seen by a nurse, doctor or genetic associate to discuss their genetic risk.
First-degree relative
A mother, brother, sister, father, son or daughter - see diagram.
Gene
A gene is a sequence of DNA. Genes are the coded instructions which determine our genetic make-up, such as eye or hair colour and also control the everyday activities of cells. Genes are made of a particular length of DNA, which consists of triplets of bases (A, C, G, T), which specify which amino acids to make, which are then built up into proteins. Thus the code for a particular protein is a specific length of DNA.
Gene cloning
A gene is isolated and copies made so that it can be studied in detail.
Genetic Counsellor
This is a member of clinical genetics unit team. Together with the medical staff they are involved with discussing genetic risk and management issues with patients. Most genetic associates have a nursing or scientific background. They may also be known as Genetic Associates or Genetic Specialist Nurses.
Genetic disease
A disease caused by a genetic fault (mutation) that is inherited or has arisen spontaneously.
Genetic engineering
Introducing new combinations of genetic material into an organism by transferring DNA not naturally occurring in the organism.
Gene expression
The process of converting genetic information into a protein.
Gene linkage map
A map of the position of genes on a chromosome. Generally genes that are inherited together are found near each other on the chromosome and are said to be linked.
Gene therapy
Treatment of a disease by introducing a new gene into a cell. The new gene may be used to replace a function that is missing because of a faulty gene.
Genetic predisposition (towards developing cancer)
An increased tendency towards developing cancer, based on the information of a strong family history and/or from genetic testing.
Genetic surveillance
The process of identifying people who are a risk of developing a specific disease or of passing such a disease on to their children.
Genetic testing
The examination of a DNA sample, to identify the structure of a specific gene to identify any significant faults (mutations).
Genome
A complete genetic sequence for a particular organism e.g. the Human Genome project.
Genotype
The DNA structure (genetic make-up) of a cell.
Germline mutation
This is a genetic fault that was inherited or developed at the time of fertilization. The mutation will then be found in all the cells in the body.
Hereditary predisposition
An increased tendency towards developing cancer, based on the information of a strong family history and/or from genetic testing.
Heterozygous
Having different forms of a gene at a certain position on a chromosome.
Histology
Relating to the tissues of the body. Written Histological (morphological) confirmation of family cancer is usually obtained from cancer registries when a family history is assessed.
Homozygous
Having identical forms of a gene at a certain position a chromosome. In a cancer cell both of the genes may be abnormal.
HNPCC
Hereditary Non-Polyposis Colorectal Cancer. A condition where polyps or lesions develop in the bowel, which may become cancerous if left untreated.
Human genome project
A project to sequence and map all the DNA in human chromosomes.
Karyotype
The chromosome content of a cell.
Locus
The position of a gene on a chromosome.
Loss of heterozygosity
The second allele of a gene is lost (by mutation). Thus, in cancer both forms of a tumour suppressor gene may become damaged, leading to loss of heterozygosity.
Malignant
The ability of a cancer cells to invade and spread.
Mammograms
Mammograms are X-rays of the breast.
Molecular testing
Examination of specific genes to detect abnormalities.
Mutation
A permanent change or alteration in the gene.
Oncogene
A gene that is capable of causing the transformation of normal cells into cancer cells. The protein product of the gene is over produced (or over expressed) which then causes pathological cell growth and division.
p53 gene
A DNA repair gene. During the cell cycle, p53 protein prevents the cell from entering the next phase until defects have been repaired. If the defects cannot be repaired, cell death is triggered by p53.
Penetrance
To do with how likely it is that a genetic mutation will cause a cancer to develop. For example in most individuals with a genetic predisposition to cancer, the gene may not be fully penetrant (about 80% penetrance) . Thus, even if an individual is a gene carrier, there is a 20% chance that they will not develop the familial cancer.
Phenotype
The characteristics of a cell.
Polymorphisms
The existence of genes at a particular position on a chromosome with an altered DNA sequence (usually non-pathological).
Polyp
A growth, often on a stalk, on a lining of the body.
Predictive test
Examination of the genes for specific mutations to assess if the individual carries a genetic fault that makes them much more likely to develop cancer than others in the near-population.
Prophylatic
Taking action to prevent a possible outcome, such as having surgery to prevent cancer occuring.
Protein
A molecule of amino acids linked together in a certain sequence as specified by the DNA sequence of a gene.
Proto-oncogene
These are genes which regulate normal cell cycles. (Oncogenes are their pathological counterparts). A mutated proto-oncogene can become an oncogene.
Recessive
A characteristic that is only apparent when there are two copies of the particular gene present, one from each parent.
Relative risk
The risk of individuals developing cancer in one group compared to those in a control group.
Second-degree relative
An aunt, uncle, cousin, grandmother or grandfather.
Somatic mutation
This is a fault that occurs after fertilization and is found only in cells that are derived from the originally mutated cell, thus only in tumour cells. In contrast, in cancer a germline mutation will be found in tumour and non-tumour cells.
Stem Cells
This type of cell has the ability to produce unlimited numbers of either new stem cells or daughter cells which will become specialised to perform a certain function.
Tumour
A growth that can be benign or malignant.
Tumour marker
An antigen that provides a measurement of tumour activity
Tumour suppressor gene
A gene that helps prevent the transformation of normal cells into cancer cells. When both copies of a tumuor suppressor gene are mutated in a cell, the lack of suppression may lead to the development of cancer.
This page was last modified on Thu Dec 02 2010
