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.

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 […]

‘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.

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 […]

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 […]

The return of stomach contents back up into the esophagus This frequently causes heartburn because of irritation of the esophagus by stomach acid. Gastroesophageal reflux disease (GERD) can lead to scarring and stricture of the esophagus, requiring stretching (dilating) of the esophagus. 10% of patients with gastroesophageal reflux disease develop Barrett’s esophagus which increases the […]

Cancer of the gland in front of the neck that normally produces thyroid hormone which is important to the normal regulation of the metabolism of the body. There are 4 major types of thyroid cancer — papillary, follicular, medullary, and anaplastic. The most common symptom of thyroid cancer is a lump, or nodule, that can […]

A thickened crescent-shaped cartilage pad in the outer portion of the joint formed by the femur (thigh bone) and the tibia (shin bone). The lateral meniscus acts as a smooth surface for the joint to move on. The lateral meniscus is toward the outer side of the knee joint. It serves to evenly load the […]

Litmus. 2. Figuratively, any test in which a single factor is decisive.

Small wingless bloodsucking insects that, along with the mite, belongs to the order Acarina. Ticks may be found in tall grass, where they may attach to a passing animal or person. Pulling a tick forcefully out from under the skin may leave the head behind. Ticks can transmit diseases such as Lyme disease, Rocky Mountain […]