• Z chromosome

    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.

  • ZAP-70

    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 […]

  • Zebra

    ‘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.

  • Zygotic lethal gene

    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 […]

  • Zygote intrafallopian transfer (ZIFT)

    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 […]

  • Bullae

    Bullae: More than one bulla, a bulla being a blister more than 5 mm (about 3/16 inch) in diameter with thin walls that is full of fluid. Blisters on the skin are called bullae. In Latin a bulla (plural: bullae) was a “bubble, stud or knob.” It referred to any rounded protrusion, particularly one that […]

  • Kernig sign

    A sign indicating the presence of meningitis (inflammation of the meninges covering the brain and spinal cord). The test for Kernig sign is done by having the person lie flat on the back, flex the thigh so that it is at a right angle to the trunk, and completely extend the leg at the knee […]

  • Corneal

    Corneal: Pertaining to the cornea, the clear front window of the eye that transmits and focuses light into the eye.

  • Hemorrhagic cyst

    This type of functional cyst occurs when bleeding occurs within a cyst. Symptoms such as abdominal pain on one side of the body may be present with this type of cyst.

  • NARP

    a disease with epilepsy, myoclonus (shock-like contraction of muscle), cerebellar dysfunction of the cerebellar portion of the brain, hearing loss and dementia; Leber’s hereditary optic atrophy — the onset in midlife (average age 30) of painless central visual loss that progresses over a period averaging 4 months, affecting both eyes affected; and Leigh’s syndrome — […]