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 earliest point.
A zygotic lethal gene is a mutated (changed) version of a normal gene essential to the survival of the zygote. The extent of the mutation can range from a change in a single base in the DNA to deletion (loss) of the entire gene.
‘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.
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 […]
- Z chromosome
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.
- Placental dystocia
Difficulty in delivering the placenta. A number of techniques may be tried to overcome placental dystocia, including changing position, massage, nursing the newborn baby to induce uterine contractions, and in some cases using medications that induce uterine contractions.
- Intraocular melanoma
An eye cancer in which the malignant cells arise in the part of the eye called the uvea. The uvea includes the iris (the colored part of the eye), the ciliary body (a muscle in the eye), and the choroid (a layer of tissue in the back of the eye). The uvea contains pigment-producing cells […]