Allele : the specific variant (nucleotide) of a polymorphism at a single locus on a chromosome; for example A, C, G or T

Amplicon : an amplified sequence of DNA generated by PCR

Cystic fibrosis : a genetically inherited disease caused by mutations in the CFTR gene, characterised by defects in ion transport affecting mucous membranes in the lung and gut

Direct sequencing : a method of determining genotype using PCR amplification and nucleotide sequencing of the amplicons generated. May not always be effective in identifying haplotypes.

DTI : Department of Trade and Industry

Factor V Leiden : Factor V Leiden thrombophilia is characterized by a poor anticoagulant response to activated protein C (APC) and an increased risk of venous thromboembolism. The term "factor V Leiden" refers to the specific G-to-A substitution at nucleotide 1691 in the gene for factor V that predicts a single amino acid replacement (Arg506Gln) at one of three APC cleavage sites in the factor Va molecule. Factor V Leiden is inactivated at a rate approximately ten times slower than normal factor V and persists longer in the circulation, resulting in increased thrombin generation and a mild hypercoagulable state reflected by elevated levels of prothrombin fragment F1+2 and other activated coagulation markers. Individuals heterozygous for the factor V Leiden mutation have a slightly increased risk for venous thrombosis; homozygous individuals have a much greater thrombotic risk

Gene Chip Microarray : a collection of microscopic dots containing oligonucleotide probes attached to a solid surface, such as glass, plastic or silicon chip forming an array. These can be used to genotype or sequence multiple regions of a genome using amplicons from patient's DNA

Genome : the entire genetic complement of an individual, representing all 46 chromosomes

Genotype : the combination of two alleles represented by a polymorphic locus on homologous chromosomes; for example in an A to G polymorphism, possible genotypes would be AA, AG or GG

Haplotype : the combination of two or more alleles at physically linked neighbouring positions within the genome

Heteroduplex : a mismatched hybrid formed between an IHG amplicon an an amplicon generated from patient's DNA

Heterozygosity : possessing different alleles on each chromosomal homolog

Homolog : 1. One member of a chromosome pair; 2. A gene similar in structure and evolutionary origin to a gene in another species; 3. In evolution, characteristics that are similar in different species because they come from a common ancestor.

Homozygosity : possessing identical alleles on both chromosomal homologs

Identifier : a series of nucleotides introduced into an IHG at a position adjacent to a polymorphic site, in order to induce the formation of an unmatched loop of DNA in heteroduplexes formed with amplicons from patient's DNA

IHG : induced heteroduplex generator

MTHFR : Hyperhomocysteinemia is a widely recognized risk factor for coronary artery disease, venous thrombosis, and stroke. It is also involved in the pathogenesis of neural tube defects, stillbirths, and recurrent pregnancy loss. One cause of hyperhomocysteinemia is mutations in the MTHFR gene

Mutation : a change in nucleotide sequence which can occur in germ line cells or somatic cells. In germ line cells, mutations can be passed on to offspring who inherit the mutation. Mutations generally have a frequency of less than 1% in the population

PCR : Polymerase Chain Reaction. A process by which a specific sequence of DNA can be amplified using iterative rounds of primer annealing, primer extension and heat denaturation.

Phenylketonuria : a genetically inherited disease caused by mutations in the PAH gene, characterised by the inability of an individual to utilise the essential amino acid, phenylalanine

Polymorphism : a variation in nucleotide sequence at a given position in the genome, seen in the population at a frequency of 1% or higher

Prothrombin : the prothrombin G20210A mutation is a common risk factor for thrombosis which increases the risk of deep vein thrombosis, stroke, and fetal loss

Reference strand conformational analysis (RSCA) : a genotyping technique in which amplicons of patient's DNA are allowed to form heteroduplexes with amplicons of known naturally occuring (reference) alleles: the resulting heteroduplexes can be separated by electrophoresis and the patterns used to indicate the patient's genotype

RFLP (Restriction Fragment Length Polymorphism) : a genotyping technique in which amplicons of patient's DNA are digested with allele-specific restriction endonucleases.

Sickle cell disease : a genetically inherited disease caused by mutations in the HBB gene, characterized by pain episodes, anaemia (shortage of red blood cells), serious infections and damage to vital organs. There are several common forms of sickle cell disease. These are called SS (individuals inherit one sickle cell gene from each parent); SC (the child inherits one sickle cell gene and one gene for another abnormal type of haemoglobin, HbC); and S-beta thalassemia (the child inherits one sickle cell gene and one gene for beta thalassemia, another inherited anaemia)

SNP (Single Nucleotide Polymorphism) : a polymorphism involving a change of a single nucleotide base within the genome

SSCP (Single-Stranded Conformational Polymorphism) : a genotyping technique in which amplicons of patient's DNA are denatured by heat, and cooled rapidly to induce the formation of intra-strand DNA duplexes. These duplexes are then separated by electrophoresis to generate genotype-specific banding patterns in nondenaturing gels

SSO (Sequence-Specific Oligonucleotide) dot : a technique whereby immobilised unlabelled amplicons are genotyped by hybridisation with a number of individual labelled homologous oligonucleotides

SSO (Sequence-Specific Oligonucleotide) reverse dot : a technique whereby labelled amplicons are genotyped by hybridisation with a number of immobilised unlabelled homologous oligonucleotides

SSP (ARMS) : a genotyping technique involving PCR amplification of patient's DNA with sequence-specific oligonucleotide primers (SSP). Amplification will only occur if the patient's DNA exactly matches the SSP. Otherwise referred to as the amplification refractory mutation system (ARMS)

Von Willebrand's disease : a genetically inherited disease caused by mutations in the VWF gene. It is the most common hereditary bleeding disorder, affecting both sexes approximately equally. Most cases are mild, and bleeding may occur after a surgical procedure or tooth extraction. The condition is worsened by the use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). Bleeding may decrease during pregnancy. The disease is very common, affecting at least 1% of the population. A family history of a bleeding disorder is the primary risk factor. In women with heavy or prolonged menstrual bleeding, Von Willebrand's is more common in Caucasian women than African American women

Wild type : the most frequently occuring allele of a polymorphic DNA sequence