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 […]

One of the National Institutes of Health in the U.S., the NHLBI’s mission is to “provide leadership for a national research program in diseases of the heart, blood vessels, lungs, and blood and in transfusion medicine through support of innovative basic, clinical, and population-based and health education research.”

A form of muscular dystrophy (MD) that is similar to Duchenne MD but milder. Patients with Becker MD produce a little of the key protein, dystrophin, whereas those with Duchenne make none. Progression of Becker MD is slower and symptoms tend to appear later than progression of Duchenne MD. Both Becker and Duchenne MD result […]

Ankle sprain: A common musculoskeletal injury in which the ligaments of the ankle partially or completely tear due to sudden stretching. This typically occurs when the ankle is suddenly “twisted” in a sports activity or by stepping off an uneven surface. The pain is initially severe and can be associated with a “popping” sensation. Immediate […]

Although the letter X can be used as a symbol in various ways (such as with X-rays, the X-axis of a graph, etc.), “the X ” in genetics and medicine today usually refers to the X chromosome. The X is the sex chromosome that is found twice in chromosomally normal females and singly along with […]

A pigmented spot on the skin, such as a mole. The plural of nevus is nevi.