Glossary of Scientific Terms

X-chromosome
One of two sex chromosomes in higher organisms that defines the gender of the adult. In almost all sexually reproducing organisms, the X-chromosome defines female characteristics.

Xenobiotics
Molecules entering an organism that has no physiological function and is not found in an organism if not taken up by eating, breathing, or injury. The term xenobiotics is used to describe a foreign particle or molecule that is potentially dangerous or toxic.  

Y-chromosome
One of two sex chromosomes in higher organisms that defines the gender of the adult. In almost all sexually reproducing organisms, the Y-chromosome defines male characteristics.  

Zebra fish
The Zebra fish is one of many model organisms used in biomedical research to understand development of higher organisms, the functioning of nervous systems, and fundamental aspects of physiology and the cause of diseases.

Zygote
A zygote is a fertilized egg containing two sets of chromosomes, one from the egg (oocyte) and one form the sperm. The zygote is a single cell and the result of a fusion between two gametes, an egg (female) and one sperm cell (male).