When a sperm enters an egg, the immediate result is known as what?

• A. Fertilization
• B. Crossing over
• C. Segregation
• D. Cytokinesis

Answer: (A)

Fertilization is the fusion of the sperm and egg that creates a zygote and restores the two sets of chromosomes, starting a new organism. When the sperm enters the egg, their haploid genomes combine to form a diploid zygote, and the egg’s metabolism is activated to begin development. This moment also sets off steps that continue after fusion, like the completion of the egg’s meiosis and the eventual merging of the pronuclei.

The other terms refer to different processes: crossing over happens during meiosis and shuffles genetic material between homologous chromosomes; segregation is the separation of chromosomes during cell division; cytokinesis is the division of the cytoplasm after mitosis or meiosis.