Fertilization is the biological process where a male gamete (sperm) and a female gamete (egg or ovum) fuse to form a new cell called a zygote, which can then develop into a new individual organism. This fusion combines the genetic material from both parents, each contributing half the number of chromosomes typical of the species, resulting in a complete set of chromosomes in the zygote
. In humans and many animals, fertilization typically occurs in the fallopian tubes, shortly after ovulation when the egg is released from the ovary. The sperm travels through the female reproductive tract to meet and penetrate the egg. The process involves several key steps:
- Sperm capacitation: the sperm undergoes changes to become capable of fertilizing the egg.
- Binding to the zona pellucida: the sperm attaches to the outer glycoprotein layer surrounding the egg.
- Acrosome reaction: enzymes from the sperm head digest the zona pellucida, allowing sperm entry.
- Fusion of sperm and egg membranes, leading to the merging of their nuclei.
- Cortical reaction: changes in the egg membrane prevent entry of additional sperm, ensuring only one fertilizes the egg
The result is an activated egg that begins cell division and embryonic development
. Fertilization is the initial step in sexual reproduction and is essential for the formation of a new organism
. In assisted reproductive technologies like in vitro fertilization (IVF), fertilization occurs outside the body in a laboratory dish, but the biological principles remain the same
. In summary, fertilization is the union of sperm and egg to form a zygote, initiating the development of a new individual
