What is a zygote?

• A. A mature egg
• B. A cell produced by mitosis
• C. An unfertilized egg
• D. The first cell formed after fertilization

Answer: (D)

A zygote is the fertilized egg—the first cell of a new individual formed when a sperm merges with an egg. It carries a complete set of chromosomes, with genetic material from both parents, making it diploid. It's different from the mature or unfertilized egg, which are the female gametes before fertilization, and from a cell produced by mitosis, which happens after fertilization to build more cells. After fertilization, the zygote immediately begins mitotic divisions (cleavage) to become a multicellular embryo.