• 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 […]

  • Artificial pacemaker

    Artificial pacemaker: A device that uses electrical impulses to regulate the heart rhythm or reproduce it. An internal pacemaker is one in which the electrodes to the heart, the electronic circuitry, and the power supply are all implanted internally, within the body. Although there are different types of pacemakers, all are designed to treat a […]

  • Advanced maternal age

    Advanced maternal age: Usually defined as age 35 or more for the mother at the time of delivery of her baby. Advanced maternal age predisposes to Down syndrome (trisomy 21). The risk of having a Down syndrome baby rises with maternal age. It essentially doubles from 1 in 725 at maternal age 32 to 1 […]

  • Board eligible

    Board eligible: In medicine, a description for a physician who has completed the requirements for admission to a medical specialty board examination but has not passed that examination. For example, a physician must have 3 years of training in an approved pediatric residency to be eligible for certification by the American Board of Pediatrics.

  • Galactosemia

    Galactosemia: An inherited disorder of galactose metabolism that occurs in newborns and can result in damage to the liver, brain, kidneys, and other organs in infants due to the accumulation of galactose derivatives in the body. Individuals with galactosemia cannot tolerate any amount of human or animal milk intake. The symptoms of galactosemia resolve if […]

  • Constrictive pericarditis

    Constrictive pericarditis: Scarring of the pericardial sac. This limits the ability of the heart to function because it cannot expand enough to collect blood and pump it to the lungs and then back to the body. Bleeding into the pericardium from trauma or from a heart operation is the most common cause of constrictive pericarditis, […]