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 grid pattern that resembles a checkerboard utilized for examination of the eye. The patient covers one eye and stares at a black dot in the center of the grid. While staring at the dot, the patient may notice that the straight lines in the pattern appear wavy. This kind of wavy pattern on viewing […]

An enema using a white, chalky solution containing barium, in preparation for series of X-ray images of the lower intestine (colon). The barium outlines the colon on the X-ray film.

1) A person trained, licensed, or skilled in nursing. 2) To feed an infant at the breast.

Fear of crossing bridges: An abnormal and persistent fear of crossing bridges. Sufferers of this phobia experience undue anxiety even though they realize their fear is irrational. Their fear may result partly from the fear of enclosure (claustrophobia) or the fear of heights (acrophobia). Phobic drivers may worry about being in an accident in busy […]

A fat that is liquid at room temperature and comes from a plant, such as olive, peanut, corn, cottonseed, sunflower, safflower, or soybean oil. Unsaturated fat tends not to raise the level of LDL (‘bad’) cholesterol in the blood.