A sex chromosome in certain animals, such as chickens, turkeys, and moths. In humans, males are XY and females XX, but in animals with a Z chromosome, males are ZZ and females are WZ.

Zeta-chain-associated protein kinase 70. A member of the protein tyrosine kinase family, ZAP-70 is normally expressed in T cells and natural killer cells and has a critical role in the initiation of T-cell signaling. ZAP-70 is expressed in T cells and tumors of T-cell lineage. A high level of ZAP-70 expression appears restricted to T-cell […]

‘When you hear hoof beats, think of horses, not zebras.’ For example, when someone develops a mild transient cough, a virus infection is the most logical and likely cause, and tuberculosis is a zebra.

A gene that is lethal (fatal) for the zygote, the cell formed by the union of a sperm (male sex cell) and an ovum (female sex cell). The zygote would normally develop into an embryo, as instructed by the genetic material within the unified cell. However, a zygotic lethal gene scotches prenatal development at its […]

A technique in which a woman’s egg is fertilized outside the body, then implanted in one of her fallopian tubes. This technique is one of the methods used to overcome infertility, the inability of couples to produce offspring on their own. First, the egg and the male sperm needed to fertilize it are harvested. Then […]

Anomaly, congenital: A birth defect. A minor congenital anomaly is an unusual anatomic feature such as a short second toe that is of no serious medical or cosmetic consequence. By contrast, a major congenital anomaly is a defect such as a cleft palate that is of serious medical or cosmetic consequence.

An infectious form of hepatitis, such as hepatitis A.

The armpit. From the Old English oxta or ohsta. The word oxter is used in certain areas of the world (Scotland, Ireland, Northern England), reminding us that there are many local and colloquial names for parts of the human anatomy. Synonymous with axilla.

Cell, beta (pancreatic): A type of cell in the pancreas (the organ of the digestive system located behind the stomach). Within the pancreas, the beta cells are located in areas called the islets of Langerhans. They constitute the predominant type of cell in the islets. The beta cells are important because they make insulin. Degeneration […]

Lung cancer that recurs in families. Lung cancer can occur sporadically in people with no known family history of lung cancer or it can recur in two or more members of the same family and constitute familial lung cancer. A gene for familial lung cancer is on the long (q) arm of chromosome 6 in […]