A sperm joins an egg cell in the process of fertilization. Because first both of the parents must contribute one gamete, then the sperm and egg unite in the process called fertilization, and finally this process forms a single celled structure called a zygote which contains the full genetic information that will be passed to the offspring. And now the offspring will have half of it's genetics from both of it's parents.
I know all of this because I just learned, studied, and took a test on this topic. Plus I checked Google just to make sure I was correct. Hope I helped you!
- Amber
