Glossary of Genetic Terminology
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NEURAL TUBE:
The embryonic structure which develops into the nervous system including the spinal cord and brain.
NEURAL TUBE DEFECTS
(NTDs):
Problems in the development of the spinal cord and brain, such as the failure of the spine to enclose the spinal cord (spina bifida) and the failure of the brain to develop (anencephaly) (see Genetics Fact Sheet 59).
NEURO-DEVELOPMENTAL:
The process of development of the brain and other parts of the central nervous system.
NEUROFIBROMATOSIS TYPE 1 (NF1):
A genetic condition where features include flat coffee-coloured 'birth marks' on the skin (cafe-au-lait patches); neurofibromas (harmless soft pink small lumps that can grow on nerves anywhere in the body); freckles in areas that are not usually exposed to sunlight; Lisch nodules (harmless small brown spots on the iris of the eye) (see Genetics Fact Sheet 37).
NEUROFIBROMATOSIS TYPE 2 (NF2):
A genetic condition characterised by the development of swellings (non-cancerous tumours called schwannomas) on the nerves that control hearing and balance (auditory and vestibular nerves) (see Genetics Fact Sheet 52).
NEURONES:
Nerve cells, the structural and functional unit of the nervous system. A neuron transmits electrical signals around the body through a network of nerve cells.
A public health funded system for testing newborn babies' blood for about 30 rare conditions. Some of these conditions can result in physical and/or intellectual problems if not treated promptly and are often referred to as inborn errors of metabolism (see Genetics Fact Sheet 20).
NONDISJUNCTION:
Where the chromosome pairs fail to separate
correctly in meiosis, resulting in sperm or egg cells which
have missing or extra chromosomes e.g. if chromosome number 21 fails to
separate in the formation of an egg (or sperm), one egg (or sperm) will contain
an extra copy of chromosome 21 (24 chromosomes) while the other egg (or sperm)
will contain only 22 chromosomes (see Genetics Fact Sheet 6).
NON-SYNDROMIC:
A condition not related to a recognised pattern of characteristics and/or symptoms (syndrome).
NUCLEOTIDES:
Please see 'Bases'.
NUCLEUS:
The structure in a cell which contains the genetic
material.