Here's why:

* Mendel's First Law: This law states that each individual carries two alleles (versions of a gene) for each trait, and these alleles separate during gamete formation (meiosis). One allele from each pair goes into each gamete.

* Chromosomes and Segregation: Chromosomes are the structures that carry genes. During meiosis, homologous chromosomes (pairs of chromosomes with the same genes) separate into different daughter cells. This separation of homologous chromosomes directly results in the separation of the alleles located on them, which is the core concept of Mendel's Law of Segregation.

In simpler terms: When a parent makes sperm or egg cells, each cell gets only one copy of each gene (one allele from the pair). This is because the chromosomes carrying those genes are separated during meiosis.