Dictionary

gastroscope A flexible, lighted instrument that is put through the mouth and esophagus to view the stomach. Tissue from the stomach can be removed through a gastroscope.

gastrostomy A surgical opening into the stomach. A gastrostomy may be used for feeding, usually via a feeding tube called a gastrostomy tube. Feeding can also be done through a percutaneous endoscopic gastrostomy (PEG) tube.

gastrostomy, percutaneous endoscopic A surgical procedure for placing a feeding tube that does not necessitate performing an open laparotomy operation on the abdomen. Abbreviated PEG. An endoscope is passed through the mouth, throat, and esophagus to the stomach. The surgeon then makes a small incision in the skin of the abdomen, pushes an IV tube…

Gaucher disease A series of disorders that are due to deficient activity of the enzyme glucocerebrosidase, which leads to accumulation of glucocerebroside in tissues of the body. The five types of Gaucher disease encompass a continuum of clinical findings from a lethal form that occurs before or just after birth to a form so mild…

gender identity disorder See transsexualism.

gene 1 In classical genetics, a unit of inheritance. 2 In molecular genetics, a sequence of chromosomal DNA that is required to make a functional product.

gene, breast cancer susceptibility See breast cancer susceptibility gene.

gene, evolutionarily conserved A gene that has remained essentially unchanged throughout evolution. Conservation of a gene indicates that it is unique and essential. Changes in the gene are likely to be lethal.

gene, target The primary gene of concern. See also gene, marker.

gene, zygotic lethal A gene that is fatal for the zygote, the cell formed by the union of a sperm and an egg. The zygote would normally develop into an embryo, as instructed by the genetic material within the unified cell. However, a zygotic lethal gene kills prenatal development at its earliest point. A zygotic…

gene deletion The total loss or absence of a gene. Gene deletion plays a role in birth defects and in the development of cancer.

gene duplication An extra copy of a gene. Gene duplication is a key mechanism in evolution. After a gene is duplicated, the once-identical genes can undergo changes and diverge to create two different genes.