• This law is also called law of purity of gametes.
• This law states that “ Two alleles of a trait (character) remain together in heterozygous condition (zygote) without combination but they remain separate or segregate at the time of gamete formation”.
• Due to segregation of alleles , gamete bear only one of the contrasting alleles.
• It means gametes are pure for a particular trait so this law is also called law of purity. Eg: Tallness(T) and dwarfness (t), two contrasting factors present in a heterozygote (Tt).
• It develops tall character but possess factors for both tall and dwarf but as soon as they get chance to separate , they segregate out. Therefore, these heterozygous produce gametes of two types and equal in no.
• Phenotypic ratio is 3:1 and genotypic ratio is 1:2:1.

• The main focused points are:

a) A character is produced by a specific gene.

b) Each gene has two alternative forms (allele).

c) The two alleles of a gene govern the development of contrasting forms of the character governed by the gene.

d) Each somatic cell of an organism has two copies of each gene.