Here's why:

* Gene pair: Each individual inherits two copies of each gene, one from each parent.

* Allele: Each copy of a gene is called an allele, and they can be the same or different.

* Gamete formation: During the process of creating sex cells (sperm and egg), the two alleles of each gene are separated.

* One allele per gamete: Each gamete receives only one allele from the pair.

In summary: The principle of segregation states that during gamete formation, the two alleles for each gene separate, and only one allele from each pair is passed on to each offspring. This ensures that each offspring inherits a complete set of genes from both parents.