Genetics Northern California


Natural history

The acquiring of medical information for an individual.

NeoplasmAn abnormal tissue that grows by cellular proliferation more rapidly than normal and continues to grow after the stimuli that initiated the new growth cease.
Neural tube

The organ which becomes the baby's brain and spinal cord. Completely formed by 5 weeks after conception. If the neural tube does not develop properly, birth defects such as spina bifida, anencephaly, and encephalocele can occur.

Neural tube defect

Birth defects which involve incomplete development of the brain, spinal cord and/or the protective coverings for these organs. Types of NTDs include spina bifida, anencephaly, and encephalocele.


Benign growths composed of fibrous and nervous tissue that usually grow just under the surface of the skin, but can also grow deeper into the body. Plexiform neurofibromas grow more diffusely and can grow around internal structures.

New mutation

Mutation that occurs for the first time in that person and is not seen in any other related family members. Also called "de novo".

Nuchal translucency (NT)

The nuchal translucency (NT) is a clear, fluid-filled area at the back of the developing baby’s neck, which can be measured by ultrasound. This fluid-filled area is larger than average in many pregnancies in which the baby has Down syndrome or another chromosome abnormality, like trisomy 18. The NT measurement can also be increased when certain physical birth defects are present, such as heart defects.


Building blocks of DNA or RNA consisting of a base(adenine, guanine, cytosine and thymine)a molecule of sugar and a phosphate group.

Null mutation

A mutation that makes no gene product at all which in turn can cause a disease state.