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 […]

Black Death: The Medieval black plague that ravaged Europe and killed a third of its population. It was due to the plague which is caused by a bacterium (Yersinia pestis) transmitted to humans from infected rats by the oriental rat flea. In 14th-century Europe, the victims of the Black Death had bleeding below the skin […]

An antiestrogen (a drug that blocks the effects of estrogen) which competes with estrogen for binding sites in target tissues such as breast. Tamoxifen has been widely publicized. It was approved by the US Food and Drug Administration (FDA) to treat breast cancer and help prevent it in women at high risk for the disease […]

A common, noncancerous enlargement of the prostate gland. The enlarged prostate may compress the urinary tube (urethra), which courses through the center of the prostate, impeding the flow of urine from the bladder through the urethra to the outside. Abbreviated BPH. If BPH is severe enough, complete blockage can occur. BPH generally begins after age […]

Empiric risk: The chance that a disease will occur in a family, based on experience with the diagnosis, past history, and medical records rather than theory.

A physician who specializes in treating diseases of the female reproductive organs and providing well-woman health care that focuses primarily on the reproductive organs.