The presence of three copies of a chromosome rather than the normal two. The most common trisomies in newborns are trisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome), and trisomy 21 (Down syndrome).
- Trisomy 13 syndrome
The presence of three copies of chromosome 13, rather than the normal two. Children with trisomy 13 syndrome are profoundly mentally retarded and have multiple malformations, commonly including scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed […]
- Trisomy 18 syndrome
The presence of three copies of chromosome 18, rather than the normal two. Children with trisomy 18 syndrome have multiple malformations and mental retardation. They characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is […]
- Trisomy 21 syndrome
A common chromosome disorder, often called Down syndrome, due to an extra chromosome number 21 (trisomy 21). The chromosome abnormality affects both the physical and intellectual development of the individual. Trisomy 21 (Down) syndrome is associated with a 45% risk for heart malformations, a lesser risk of duodenal atresia (part of the small intestines is […]
Hydrogen-3, an isotope of hydrogen. Tritium is a long-lived weak emitter of radiation and can be easily incorporated in large molecules such as DNA, and is therefore much used for autoradiography in the laboratory.
A sharply pointed shaft, usually with a three-sided point. A trocar may be used within a cannula, a hollow tube, designed to be inserted into a vein, artery, bone marrow or body cavity. The word trocar is derived from the French “trois” (three) + “carre” (side).