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.
One of the stages of chronic obstructive lung disease (COPD), according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD). GOLD-3 is stage III in the GOLD classification of COPD and indicates “severe COPD.” This stage is characterized by severe airflow limitation or the presence of respiratory failure or clinical signs of right heart […]
- Coitus interruptus
Coitus interruptus: A method of contraception, also called withdrawal, in which the man withdraws his penis from the vagina before ejaculation. Fertilization is prevented because the sperm do not enter the vagina. The effectiveness of this maneuver depends on the man’s ability to withdraw before the ejaculation of any sperm. Withdrawal does not provide protection […]