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 […]

Fertility awareness: Also known as natural family planning, periodic abstinence and the rhythm method, this approach entails not having sexual intercourse on the days of a woman’s menstrual cycle when she is most likely to become pregnant or using a barrier method (such as a condom, the diaphragm or a cervical cap) for birth control […]

Characteristic of 95 percent of values from a normal population. The remaining normal results fall outside the normal range, as do any truly abnormal results. The normal range for a particular test result, condition, symptom, or behavior may differ, based on the patient’s age, size, sex, ethnicity, or culture.

An autosomal recessive form of hereditary spastic paraplegia with dementia first described in the Old Order Amish. The disease usually surfaces in early adulthood and is slowly progressive. The Mast syndrome gene is in chromosome 15q22.31 Its protein product is called maspardin.

Dystonia, Segawa: An important variant form of dopa-responsive dystonia (DRD). DRD typically begins in childhood or adolescence with progressive difficulty in walking and, in some cases, with spasticity. DRD, by definition, can be successfully treated with dopa. In Segawa dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse […]

An acute highly contagious viral disease with fever, runny nose, cough, red eyes, and a spreading skin rash, the measles (also known as rubeola) is a potentially disastrous disease. It can be complicated by ear infections, pneumonia, encephalitis (that can cause convulsions, mental retardation. and even death), the sudden onset of low blood platelet levels […]