• 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 […]

  • Hepatitis G

    A virus isolated from the blood of some patients with posttransfusion hepatitis that is hypothesized to be a cause of hepatitis by some investigators, but the virus has not yet been confirmed as a cause of acute or chronic hepatitis.

  • Evolutionarily conserved gene

    Evolutionarily conserved gene: A gene that has remained essentially unchanged throughout evolution. Conservation of a gene indicates that it is unique and essential: There is not an extra copy of that gene with which evolution can tinker, and changes in the gene are likely to be lethal.

  • Cardiac aneurysm

    Cardiac aneurysm: An outpouching of an abnormally thin portion of the heart wall. Cardiac aneurysms tend to involve the left ventricle because the blood there is under the greatest pressure.

  • Ion channel

    A protein that acts as a pore in a cell membrane and permits the selective passage of ions (such as potassium ions, sodium ions, and calcium ions), by means of which electrical current passes in and out of the cell. Ion channels also serve many other critically important functions including chemical signalling, transcellular transport, regulation […]

  • Antidepressant, tricyclic

    Antidepressant, tricyclic: One of a class of medications used to treat depression. The tricyclic antidepressants (TCAs) are also used for some forms of anxiety, fibromyalgia, and the control of chronic pain. “Tricyclic” refers to the presence of three rings in the chemical structure of these drugs.