Genetics - A branch of biology that studies heredity and variation in organisms.⏎
Fertilized Egg - Sometimes referred to as a zygote, this is the resulting initial cell formed when a sperm cell unites with an egg cell.⏎
Contagion - A general term for any disease-causing infectious agent spread by direct or indirect contact.⏎
Egg Cell - The female gamete, or sex cell, which carries the hereditary material of the female parent and unites with the male sperm cell during sexual reproduction.⏎