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 […]

(1902-1992) American geneticist who won the 1983 Nobel Prize in Physiology or Medicine for her discovery of genetic transposition, or the ability of genes to change position on the chromosome. Barbara McClintock was born in Hartford, Connecticut. Her family moved to Brooklyn, New York, in 1908. McClintock earned her B.S. and M.S. degrees in botany […]

Scar tissue in the macula, the area of the retina responsible for sharp central vision. The scar can blur and distort vision and make straight lines appear wavy. Macular pucker is due most often to age-related shrinkage of the vitreous which pulls away from the retina, causing the retina to scar and wrinkle. Other causes […]

Agranulocytosis, infantile genetic: Children born with this condition lack neutrophils (a type of white blood cell that is important in fighting infection). These children suffer frequent infections from bacteria which in the past led to death in three-quarters of cases before 3 years of age. This disease is also known as severe congenital neutropenia (SCN). […]

A salivary gland that is located under the floor of the mouth, close to the midline. The sublingual gland is the smallest of the three major salivary glands (the parotid, submandibular, and sublingual glands).

Gene, regulatory: A gene that regulates the expression of other genes. A regulatory gene is a nosy gene whose prime preoccupation is to horn in on other genes and control the rate at which they make products.