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 […]

Endovaginal ultrasound: This type of imaging test is a special form of ultrasound developed to examine the pelvic organs and is the best test for diagnosing an ovarian cyst. A cyst can be diagnosed based on its appearance on the ultrasound. An endovaginal ultrasound is a painless procedure that resembles a pelvic exam. A thin, […]

Auditory acuity: The clarity or clearness of hearing, a measure of how well a person hears. Auditory acuity is measured in order to determine a person’s need for a hearing aid.

An embolus of microscopic size. For example, a tiny blood clot or little clump of bacteria. Like any embolus, it travels through the bloodstream, lodges in a blood vessel and blocks it.

The normal regular rhythm of the heart set by the natural pacemaker of the heart called the sinoatrial (or sinus) node. It is located in the wall of the right atrium (the right upper chamber of the heart). Normal cardiac impulses start there and are transmitted to the atria and down to the ventricles (the […]

The sum of the genetic information contained in the chromosome of the mitochondrion, a structure located in the cytoplasm outside the nucleus of the cell. The mitochondrial genome is composed of mitochondrial DNA (mDNA), a double-stranded circular molecule that contains a limited number of genes. During fertilization, mDNA is transmitted only by the mother. Together, […]