• 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 […]

  • Laser-assisted in situ keratomileusis

    A kind of laser eye surgery designed to change the shape of the cornea to eliminate or reduce the need for glasses and contact lenses in cases of severe myopia (nearsightedness). The procedure is best known as LASIK, an acronym for laser-assisted in situ keratomileusis. Before LASIK, the most common form of laser eye surgery […]

  • p arm of a chromosome

    The short arm of a chromosome. The “p” comes from the French “petit” meaning small. All human chromosomes have 2 arms – the p (short) arm and the q (long) arm – that are separated from each other only by a primary constriction, the centromere, the point at which the chromosome is attached to the […]

  • Chronic fatigue syndrome

    A debilitating and complex disorder characterized by profound fatigue that lasts 6 months or longer, is not improved by bed rest, and may be worsened by physical or mental activity. Abbreviated CFS. Persons with CFS most often function at a substantially lower level of activity than they were capable of before the onset of the […]

  • Rheumatoid factor

    An antibody that is measurable in the blood and is used to diagnose rheumatoid arthritis. Rheumatoid factor is present in about 80 percent of adults, and a much lower proportion of children, who have rheumatoid arthritis. It is also present in patients with other connective-tissue diseases, such as systemic lupus erythematosus, and in some patients […]

  • Turcot syndrome

    A genetic disease characterized by polyps in the colon (large intestine) in addition to tumors in the brain. The polyps in the colon tend to become malignant. The brain tumors are also malignant. Skin abnormalities can also occur. Turcot syndrome is inherited in an autosomal recessive manner and can result from mutations in either the […]