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 condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Smoldering leukemia also is called myelodysplastic syndrome or preleukemia.

Problems that occur when treatment goes beyond the desired effect. Or problems that occur in addition to the desired therapeutic effect. Example — A hemorrhage from the use of too much anticoagulant (such as heparin) is a side effect caused by treatment going beyond the desired effect. Example — The common side effects of cancer […]

The ability of bacteria and other microorganisms to resist the effects of an antibiotic to which they were once sensitive. Antibiotic resistance is a major concern of overuse of antibiotics. Also known as drug resistance.

A sudden involuntary contraction of the muscular wall of the bladder causing urinary urgency, an immediate unstoppable need to urinate. It is a form of urinary incontinence (the unintentional loss of urine) and affects about 1 in 11 adults, particularly older adults. Treatment may include pelvic muscle strengthening, behavioral therapy, and medications. Also called urge […]

Also called a hypnagogic hallucination, this type of dream is characteristically vivid and occurs as one is falling asleep or awakening.