• 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 […]

  • Micturition

    Urination; the act of urinating.

  • OPCA

    Olivopontocerebellar atrophy.

  • Palsy, Bell’s

    Paralysis of the nerve that supplies the facial muscles on one side of the face (the seventh cranial nerve, or facial nerve). Bell’s palsy often starts suddenly. The cause may be a viral infection. Treatment includes protecting the eye on the affected side from dryness during sleep. Massage of affected muscles can reduce soreness. Sometimes […]

  • Biliary atresia

    Biliary atresia: Congenital absence or closure of the major bile ducts, the ducts that drain bile from the liver. Biliary atresia results in a progressive inflammatory process which may lead to cirrhosis of the liver. The infant looks normal at birth but develops jaundice after the age of 2 to 3 weeks with yellowing of […]

  • Mycobacterium ulcerans

    The bacterium that causes Buruli ulcer. Mycobacterium ulcerans is a member of the family of bacteria that causes tuberculosis and leprosy.