Fertilisation occurs when which part of the sperm and the egg cell fuse?

Fertilisation occurs when the nucleus of the sperm cell and the nucleus of the egg cell fuse. Here are the steps:

1. The sperm cell, after a long journey, reaches the egg cell in the female reproductive system.

2. The head of the sperm cell, which contains the nucleus, penetrates the outer layers of the egg cell.

3. Once the sperm cell has successfully penetrated these layers, the nuclei of the sperm and egg cells come into contact.

4. The genetic material (DNA) from the sperm cell's nucleus merges with the genetic material from the egg cell's nucleus.

5. This fusion of nuclei, and therefore fusion of genetic material, is what we refer to as fertilisation.

6. The result is a single cell, known as a zygote, which contains a combination of genetic material from both parents. This zygote will begin to divide and grow into an embryo.