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 […]

A vaccine designed to prevent rubella, or German measles. German measles was once seen merely as a child’s unpleasant rite of passage. It was thought to be a mild malady that was usually over and done in three days. So what? Then an outbreak of rubella began in 1964. It lasted two years and infected […]

A laparoscopic adjustable gastric band, commonly referred to as a lap band, is an inflatable silicone device surgically implanted around the top portion of the stomach to help a person lose weight. A band is placed around the upper part of the stomach, creating a small pouch that can hold only a small amount of […]

Atrium: An entry chamber. On both sides of the heart, the atrium is the chamber that leads to the ventricle.

A test in which a small drop of the suspected allergy-provoking substance (allergen) is placed on the skin and the skin is then gently scratched through the drop with a sterile needle. If the skin reddens and, more importantly, if it swells, the test is read as positive, and allergy to that substance is considered […]

An uncommon eye cancer that arises in the conjunctiva, the clear membrane that covers the outer surface of the eye and the inner part of the eyelids. Conjunctival melanoma accounts for 2% of all eye malignancies and tends, like melanoma of the skin, to occur in light skinned people. Features of the disease include fixation […]