• 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 […]

  • Bulimia nervosa

    See Bulimia.

  • WPW syndrome

    Wolff-Parkinson-White syndrome.

  • UAG

    A triplet consisting of uracil, adenine, guanine, in that order, that acts as a stop codon in messenger RNA (mRNA), signaling the termination of translation of an mRNA molecule and the release of the nascent polypeptide chain.

  • Cerebrovascular disease

    Cerebrovascular disease: Disease of the blood vessels and, especially, the arteries that supply the brain. Cerebrovascular disease is usually caused by atherosclerosis and can lead to a stroke. See also atherosclerosis, stroke.

  • Nurse-midwifery

    The practice engaged in by a nurse-midwife in the management of women’s healthcare, particularly pregnancy and childbirth.