Glossary of Cancer Genetics

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Disclaimer: this glossary has been written for educational purposes only, it can not be used for diagnosing or treating a health problem or a disease. If you have or suspect you may have a health problem, you should consult your doctor. No responsibility can be accepted for information on any linked page, please read the provider's own disclaimer where appropriate.

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About this glossary: The glossary is part of Cancer GeneticsWeb
There are currently 31 definitions in the database
This file generated from glossary.dbf at Wed 7 Feb 2001

About the author: hello, my name is Simon Cotterill , I work in the North of England Children's Cancer Research Unit, based in the Department of Child Health at The University of Newcastle, UK. I have been involved in cancer research since 1989, my speciality is computing and statistical analysis, my qualifications are non-medical. This glossary has been developed largely in my personal time, any mistakes in this guide are entirely my own. Feedback

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How to use this glossary
  1. In the top frame click on the first letter of the word you are interested in. load frame set
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[Genes] displays an alphabetical list of cancer related genes.
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Adenine
A nitrogen rich base which is one of the buiding blocks of DNA. It is one member of the base pair A-T (adenine-thymine)

See also: Base Pair
See also: Thymine

Allele
Alternative forms of a gene. A single allele is inherited seperately from each parent.

See also: Gene.

Amplification
An increase in the number of copies of a specific DNA fragment (amplicon). For example the MYCN oncogene is often amplified in neuroblastoma.

See also: Mutation.

Autosome
A chromosome not involved in sex determination. In a normal human cells there 22 pairs of autosomes.

See also: Chromosome.
See also: Sex-Chromosome

Base Pair
Two nitrogen rich bases heald together by weak chemical bonds: adenine and thymine (A-T) or guanine and cytosine (C-T). Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs.

See also: Adenine
See also: Thymine
See also: Guanine
See also: Cytosine
See also: DNA (deoxyribonucleic acid)

Caretaker gene
A class of genes that when inactivated do not directly promote tumours; instead their inactivation results in genetic instabilities causing an increased mutation rate affecting all genes including gatekeeper genes, which do directly regulate tumour growth. BRCA1 and BRCA2 are examples of caretaker genes.

See also: Gatekeeper gene

Chromosome-Abnormalities
Changes in the number or structure of the chromosomes in a cell. These can be classed as: Numeric Alterations where one or more whole chromosomes are lost or extra chromosomes are gained, or Structural Alterations where the structure of one or more chromosomes is changed. There are many types of structural alterations including partial chromosome deletions, partial gains and translocations.

See also: Chromosome.
See also: Translocation
See also: Mutation.
* Chromosome Menu

Chromosome.
Structures composed of DNA including genes, located in the nucleus of a cell. A normal diploid human cell contains 46 paired chromosomes; 22 pairs of autosomes (chromosomes 1 to 22) and 2 sex chromosomes (XX in females, XY in males). Cancer cells often contain chromosome abnormalities.

See also: DNA (deoxyribonucleic acid)
See also: Gene.
See also: Chromosome-Abnormalities
* Chromosome Menu

Cytosine
A nitrogen rich base which is one of the buiding blocks of DNA. It is one member of the base pair G-C (guanine-cytosine)

See also: Base Pair
See also: Guanine

DNA (deoxyribonucleic acid)
The molecule which encodes genetic information. It is a double-stranded molecule composed of nucleotide base pairs. The nucleotides are adenine (A), guanine (G), cytosine (C) and thymine (T). Base pairs form between A and T and between G and C. It is the weak chenical bonds between bases which hold the two strands of DNA together in the shape of a double helix.

See also: Base Pair
See also: Adenine
See also: Guanine
See also: Cytosine
See also: Thymine
See also: Gene.

Familial Cancer
Cancer, or a predisposition towards cancer, that runs in families. Familial cancer account for approximately 5-10% of cancers overall. In general this involves several members of a family developing the same type of cancer, typically it develops at an earlier age than sporadic (non-inherited) cancers. The cancer may be due to an inherited gene mutation. For example the BRCA1 gene is mutated in some families with hereditary breast and ovarian cancers.

Cancer is common (1 in 3 people develop cancer) so a number of people with cancer in the same family does not necessarily imply the cancer is hereditary. If you are worried you have a familial cancer you should discuss this with your doctor.

See also: Hereditary-Mutation
See also: Mutation.

Gatekeeper gene
A class of genes which directly regulate tumour growth by inhibiting growth or by promoting cell death. TP53 is a prime example.

See also: Caretaker gene

Gene.
The fundamental unit of hereditary. Genes are composed of nucleotides in a specific order which codes a protein or RNA molecule. There are 50,000 to 80,000 genes in humans each serving specific functions. Each genes is located in a paricular position in a paricular chromosome.

See also: Nucleotide
See also: Chromosome.
See also: Protein
See also: Tumour-Supressor Gene
See also: Oncogene

Germline Mutation


See also: Hereditary-Mutation

Guanine
A nitrogen rich base which is one of the buiding blocks of DNA. It is one member of the base pair G-C (guanine-cytosine).

See also: Base Pair
See also: Cytosine

Hereditary-Mutation
An inherited genetic mutation which is present in all the cells of an individual. Overall, approximately 5-10% of human cancers are hereditary.

See also: Familial Cancer
See also: Mutation.
See also: Somatic Mutation

Kilobase (Kb)
Unit of DNA length. 1 Kb = 1 thousand nucleotides.

See also: Nucleotide

Megabase
Unit of DNA length. 1 Mb = 1 million nucleotides.

See also: Nucleotide

Mutation.
A change in the DNA base pair sequence. Gene mutations can be hereditary or somatic (non-hereditary). Certain mutations can cause or contribute to cancer development. For example hereditary mutations of the TP53 gene are found in Li-Faumeni syndrome (a family cancer syndrome). The vast majority (90-95%) of cancers are non-hereditary. A cells DNA may acquire somatic mutations, for example after exposure to a carcinogen, and accumulated mutations can cause cancer. There are many different types of mutations.

See also: Hereditary-Mutation
See also: Somatic Mutation
See also: Point Mutation
See also: Amplification
See also: Chromosome-Abnormalities

Nucleotide
A subunit of DNA or RNA consisting of one base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), plus a phosphate molecule, and a sugar molecule (deoxyribose in DNA and ribose in RNA). Thousands of nucleotides are linked to form a DNA or RNA molecule.

See also: DNA (deoxyribonucleic acid)
See also: RNA (Ribonucleic Acid)

Oncogene
Mutated forms of genes (proto-oncogenes) which promote abnormal growth and cell division. Examples include KRAS, BCL1, and C-MYC which are involved in a range of different cancers.

Penetrance
The likelihood that a given allele will actually result in disease. If a mutated allele is fully penetrant this means all individuals who have this mutation will develop the disease.

See also: Allele
See also: Mutation.

Point Mutation
A single change in a base pair sequence. Such small changes can sometimes cause a gene to loose or change its function.

See also: Mutation.

Polymorphism
Difference in a DNA sequence occurring among individuals. These are considered normal genetic variations which contribute to our individual characteristics rather than gene mutations. Certain polymorphisms may increase a person's susceptibility to cancer. For example, these small genetic differences might explain why some smokers develop lung cancer while others do not.

See also: Mutation.
* Genetic Epidemiology

Protein
A large molecule composed of one or more chains of amino acids set out in a specific order which is determined by the gene which codes it. Proteins are required for the structure, function, and regulation of cells, tissues, and organs. There are thousands of different proteins serving specific functions in the body.

See also: Gene.

RNA (Ribonucleic Acid)
A molecule which plays an important role in protein synthesis and other chemical activities of the cell. RNA is composed of nucleotides and is very similar to DNA in structure. There are several different types of RNA.

See also: DNA (deoxyribonucleic acid)
See also: Nucleotide
See also: Protein

Sex-Chromosome
Chromosomes X and Y determine the sex of an individual. Males have an X and a Y chromosome while females have 2 X chromosomes.

See also: Chromosome.
See also: Autosome

Somatic Mutation
Genetic changes arising in individual cells, not hereditary. A number of somatic mutations in different genes may be necessary for cancer to develop, a "multi-step" process.

See also: Mutation.
See also: Hereditary-Mutation

Thymine
A nitrogen rich base which is one of the buiding blocks of DNA. It is one member of the base pair A-T (adenine-thymine).

See also: Base Pair
See also: Adenine

Translocation
Movement of a chromosome fragment to another place. Translocations are common in sarcomas and leukaemias. For example Ewing's sarcoma is characterised a t(11;22) translocation which fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11.

See also: Chromosome.

Tumour-Supressor Gene
Genes which normally function to inhibit cell growth/division and prevent cancer. If a tumour supressor gene is deleted or becomes mutated this can contribute to cancer development. Examples include the BRCA1 gene which is mutated in some breast cancers and RB1 which is mutated in retinoblastoma.

See also: Gene.


First created: Sun 17 Sep 2000
Last modified: Wed 7 Feb 2001