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 […]

Exaggerated startle disease: A genetic disorder also known as hyperexplexia in which babies have an exaggerated startle reflex (reaction). This disorder was not recognized until 1962 when it was described by Drs. Kok and Bruyn as a disease with the onset at birth of hypertonia (stiffness), exaggerated startle response, strong brain-stem reflexes (especially head-retraction reflex) […]

A prefix derived from the Greek “pathos” meaning “suffering or disease.” Patho- serves as a prefix for many terms including pathogen (disease agent), pathogenesis (development of disease), pathology (study of disease), etc. The corresponding suffix is -pathy.

Commonly called “the pill,” combined oral contraceptives are the most commonly used form of reversible birth control in the United States. This form of birth control suppresses ovulation (the monthly release of an egg from the ovaries) by the combined actions of the hormones estrogen and progestin. If a woman remembers to take the pill […]

A surgical procedure using a donor kidney to treat kidney failure. Transplantation is a preferred treatment over dialysis because of its improved outcomes. The principal problems in kidney transplantation are immunologic, i.e. avoiding rejection of the transplanted kidney by the recipient’s immune system. The first kidney transplant was done in Boston by surgeon Joseph E. […]

Migraine involving the eyes but without headache. Migraine, due to a spasm of blood vessels in the brain, usually causes a headache. Flashes of light may appear as jagged lines or “heat waves” in one or both eyes and often last 10-20 minutes, sometimes without a headache. This is termed ophthalmic migraine, or migraine without […]