Glossary of terms used on this site

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Term Definition

A device that supports and stabilises the arches of the foot and helps to align the ankle and foot.

De novo (gene) mutation

New mutation. An alteration in a gene that is present for the first time in one family member as a result of a mutation in a gamete (egg or sperm) of one of the parents or in the fertilized egg itself.

Degenerative disorder

A disease in which the function or structure of the affected tissues or organs changes for the worse over time.

Degree of relationship

The degree of relationship helps define the proportion of genes shared by two blood relatives.

Descending colon

The ascending colon runs from the end of the small intestine and up the right-hand side of the abdomen.

Detached retina

The retina is a thin layer of nerve cells lining the inside of the back of the eye. You need the retina to see properly. It turns the light that enters the eye into an image by sending a message along the optic nerve to the brain.

Developmental delay

Delays in any or all areas including cognitive, social, language, sensory, and emotional development.


A local council grant to help towards the cost of adapting your home to enable you to continue to live there. A grant is paid when the council considers that changes are necessary to meet your needs - and is happy that the work is reasonable and practical.


Diabetes mellitus is a condition in which the amount of glucose (sugar) in the blood is too high because the body cannot use it properly. There are two main types of diabetes that result when either the body is unable to produce any insulin (Type 1) or Type 2, when the body can still make some insulin (but not enough), or when the insulin that is produced does not work properly.

Diabetes type 2

Diabetes is a chronic condition caused by a higher than normal level of glucose in the blood. In type-2 (or ‘non-insulin dependent’) diabetes the body does not make enough insulin or is unable to use it properly. Symptoms are often controlled through diet.


The foods a person eats in the course of a day or week. The more balanced and nutritious the diet, the healthier the person can expect to be.

Direct mutation detection

The use of a laboratory method (such as sequence analysis) directly on DNA to detect an alteration

Disability living allowance

Disability Living Allowance, sometimes referred to as DLA, is a tax-free benefit for children and adults who need help with personal care or have walking difficulties because they are physically or mentally disabled.

Dislocated lenses

When the lens (the transparent structure at the front of your eye) falls into an abnormal position.


Having a pair of chromosomes (two copies).

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