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 […]

Empirical: Based on experience and observation rather than on systematic logic. Experienced physicians often use empirical reasoning to make diagnoses, based on having seen many cases over the years. Less-experienced physicians are more likely to use diagnostic guides and manuals. In practice, both approaches (if properly applied) can lead to the same diagnosis.

Drug, sulfa: One of the sulfonamides, the sulfa-related antibiotics which are used to treat bacterial and some fungal infections. The first sulfa drug was prontosil. It was discovered by the German physician and chemist Gerhard Domagk in 1935. The sulfa family of drugs includes sulfadiazine, sulfamethizole (brand name: Thiosulfil Forte), sulfamethoxazole (Gantanol), sulfasalazine (Azulfidine), sulfisoxazole […]

Benzo(a)pyrene: Abbreviated B(a)P. A member of a class of compounds known as polycyclic aromatic hydrocarbons (PAHs). The metabolites of B(a)P are mutagenic and highly carcinogenic. When the body tries to metabolize B(a)P, the resulting compounds react and bind to DNA which results in mutations and eventually cancer.

A funnel shaped piece of plastic on a light source that is inserted into the auditory canal of the ear, allowing the examiner to look at the ear canal and ear drum. The auditory canal begins at the circular opening of the ear and continues a distance of about one inch [about 2 1/2 cm] […]

Beard ringworm: A superficial fungal infection of the skin, affecting the bearded area of the face and neck, with swellings and marked crusting, often with itching, sometimes causing the hair to break off. In the days when men went to the barber daily for a shave, this affliction was called barber’s itch. Also known as […]