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 […]

Deuterium: A non-radioactive isotope of hydrogen that contains a neutron in its nucleus in addition to the one proton normally seen in hydrogen. A deuterium atom is twice as heavy as normal hydrogen.

Also known as giant cell pneumonia, this is a deadly but fortunately rare complication of measles. It tends to strike children who are immunodeficient as from leukemia or HIV/AIDS. The postmortem examination (autopsy) shows multinucleated giant cells lining the alveoli (air sacs) of the lungs. Named for the early 20th-century Austrian pathologist Victor Hecht.

Case-to-infection ratio: The ratio of the number of cases of a disease compared to the number of infections with the agent that causes the disease. Also called the case-to-infection proportion.

Syphilis. Depending upon someone’s thoughts as to where the disease came from, syphilis was also known as the French, Spanish, German and Polish disease.

On a prescription, every two hours.