Which law states that traits are determined by pairs of alleles that segregate during meiosis?

The correct answer is the Law of Segregation, which was first proposed by Gregor Mendel in his studies of inheritance in pea plants. This law states that during the formation of gametes, the alleles for a trait separate so that each gamete only carries one allele for each gene. This segregation occurs during meiosis, where homologous chromosome pairs are separated into different gametes, ensuring that offspring inherit one allele from each parent.

This principle is crucial in understanding genetic inheritance, as it explains how traits can be passed down and how variation occurs in a population. The segregation of alleles leads to combinations that contribute to the diversity of traits observed among individuals. The Law of Segregation is a foundational concept in genetics, forming the basis for further understanding of more complex inheritance mechanisms.