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 […]

Any disease that affects the progress of bone growth by killing bone tissue. Osteochondrosis is seen only in children and teens whose bones are still growing.

A disorder due to the cancer treatment retinoic acid characterized by fever, difficulty breathing, chest pain, lung infiltrates, fluid around the lungs and heart, and hypoxia (lack of oxygen) that develops in some patients receiving retinoic acid therapy. It usually develops within 30 days of treatment. Steroids and chemotherapy can be used to treat retinoic […]

The identification of the genes that influence social behavior, the understanding of the influence of these genes on underlying neural and endocrine mechanisms, and the exploration of the effects of the environment — particularly the social environment — on gene action. The term “sociogenomics” is a new one. Sociogenomics is related to the established field […]

Caudal: An anatomic term meaning 1. Pertaining to the tail or the hind part. 2. Situated in or directed toward the tail or hind part. 3. Inferior to another structure, in the sense of being below it. Caudal is also short for caudal epidural anesthesia. The terms caudal and caudad are both derived from the […]

Cranial nerve, fourth: The fourth cranial nerve, the trochlear nerve, is the nerve supply to the superior oblique muscle of the eye, one of the muscles that moves the eye. Paralysis of the trochlear nerve results in rotation of the eyeball upward and outward (and, therefore, double vision). The twelve cranial nerves, the trochlear nerve […]