The law of segregation is a key principle of Mendelian inheritance that dictates how alleles separate during the formation of gametes.

Specifically, the law of segregation, also known as Mendel’s First Law, was introduced by Gregor Mendel in 1865. This law states that each individual organism possesses two alleles for each trait, which segregate (or separate) from one another during gamete formation. Consequently, each gamete contains only one allele from each pair.

In the framework of Mendelian inheritance, this law clarifies how traits are transmitted from parents to their offspring. During reproduction, an organism passes one of its two alleles to its offspring. If the alleles in a pair are different (i.e., the organism is heterozygous), one allele is dominant while the other is recessive. The dominant allele will mask the effect of the recessive allele, resulting in the expression of the trait associated with the dominant allele.

For instance, consider a pea plant that is heterozygous for seed color, possessing one allele for yellow seeds (the dominant allele) and one for green seeds (the recessive allele). According to the law of segregation, these two alleles will separate during the formation of gametes. The resulting gametes will each carry one allele for seed color—either yellow or green. When these gametes unite during fertilization, the offspring will inherit one allele from each parent, ultimately determining the color of their seeds.

In summary, the law of segregation is a foundational principle of Mendelian inheritance that elucidates how traits are transmitted across generations. It provides a crucial framework for understanding the distribution of traits within a population and serves as the basis for the field of genetics.