• 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 […]

  • Keshan disease

    A condition caused by deficiency of the essential mineral selenium. Keshan disease is a potentially fatal form of cardiomyopathy (disease of the heart muscle). It was first observed in Keshan province in China, and it has since been found in other areas where the selenium level in the soil is low. Treatment involves selenium supplementation.

  • T-helper cell

    those that activate other T cells to achieve cellular inflammatory responses; and those that drive B cells to produce antibodies in the humoral immune response. These two classes of response are generally incompatible with one another and require coordination by substances called cytokines to promote one response while dampening the other. The HIV virus attacks […]

  • Contractions, Braxton Hicks

    Contractions, Braxton Hicks: Irregular contractions of the womb (the uterus) occurring towards the middle of pregnancy in the first pregnancy and, earlier and more intensely, in subsequent pregnancies. These contractions tend to occur during physical activity. The uterus tightens for 30 to 60 seconds beginning at the top of the uterus; and the contraction gradually […]

  • Conjugated linoleic acid

    Conjugated linoleic acid: (CLA) A supplement that has been promoted as an aid to weight loss and muscle building and as a deterrent to heart disease, diabetes and cancer. CLA is an unsaturated fatty acid in the milk and meat of cows, sheep and goats. CLA occurs in about 20 different chemical configurations called isomers, […]

  • Pit, ear

    A tiny pit in front of the ear, also called a preauricular pit. This minor anomaly is of no consequence in and of itself. It is more common in blacks than in whites, and in females than males. It can recur in families. However, the presence of two or more minor anomalies such as this […]