Gene testing Health Dictionary

The functional unit of heredity. A segment of DNA (or RNA in certain viruses) that encodes a single protein or confers a specific trait.... gene

Gene therapy is the transfer of normal GENES into a patient to combat the effects of abnormal genes which are causing disease(s). The GENETIC ENGINEERING technique used is SOMATIC cell gene therapy in which the healthy gene is put into somatic cells that produce other cells – for example, stem cells that develop into BONE MARROW. Descendants of these altered cells will be normal and, when su?cient numbers have developed, the patient’s genetic disorder should be remedied. The abnormal gene, however, will still be present in the treated individual’s germ cells (eggs or sperm) so he or she can still pass the inherited defect on to succeeding generations.

Gene therapy is currently used to treat disorders caused by a fault in a single recessive gene, when the defect can remedied by introducing a normal ALLELE. Treating disorders caused by dominant genes is more complicated. CYSTIC FIBROSIS is an example of a disease caused by a recessive gene, and clinical trials are taking place on the e?ectiveness of using LIPOSOMES to introduce the normal gene into the lungs of someone with the disorder. Trials are also underway to test the e?ectiveness of introducing tumour-suppressing genes into cancer cells to check their spread.

Gene therapy was ?rst used in 1990 to treat an American patient. Eleven European medical research councils (including the UK’s) recommended in 1988 that gene therapy should be restricted to correcting disease or defects, and that it should be limited to somatic cells. Interventions in germ-line cells (the sperm and egg) to e?ect changes that would be inherited, though technically feasible, is not allowed (see CLONING; HUMAN GENOME).... gene therapy

A gene that produces a GENOTYPE which causes the death of an organism before that organism has reproduced – or which prevents it from reproducing. Lethal genes are usually RECESSIVE, so the organism will die only if both its ‘parents’ carry the gene. Should only one parent have the lethal gene, its consequences will be masked by the dominant ALLELE passed on by the normal parent.... lethal gene

See under GENETIC DISORDERS.... autosomal dominant gene

In surveys, studying the process of interpretation of questions and the formation and reporting of responses by respondents to learn how to make the questions more accurately obtain the data the questionnaire is seeking.... cognitive testing

See GENETIC DISORDERS.... dominant gene

The full use of the information in a gene via transcription and translation leading to production of a protein.... gene expression

A series of exercises designed to determine an individual’s level of fitness, primarily cardiovascular fitness and muscle performance. Fitness testing is often carried out before a person starts an exercise programme to evaluate its safety and suitability or to monitor progress thereafter.

A physical examination is usually performed, including measurement of body fat, height, and weight. Blood and urine tests may be done, including an analysis of blood cholesterol. The performance of the heart is measured by taking the pulse before, during, and after aerobic exercise. Another test involves measuring a person’s overall performance in a standard exercise. (See also aerobics; exercise.)... fitness testing

The use of blood tests to help decide whether a man is the father of a child.

Blood samples are taken from the child, from the suspected father, and sometimes from the mother.

The samples are tested for blood groups, histocompatibility antigens, and similarities in DNA.

Genetic fingerprinting provides the most decisive result.... paternity testing

see clone.... gene clone

a gene that prevents the expression of another (non-allelic) gene.... suppressor gene