Phenotypic ratio 3:1 proves Segregation

Phenotypic ratio refers to the ratio of observable traits in the offspring of a cross between two individuals. In genetics, a 3:1 phenotypic ratio indicates that three-fourths of the offspring display one phenotype, while one-fourth displays the other phenotype. This ratio is observed in a monohybrid cross between two heterozygous individuals.

Segregation is a fundamental principle of genetics proposed by Gregor Mendel. According to this principle, each individual has two copies of each gene, which are separated during gamete formation. When gametes combine during fertilization, each offspring inherits one copy of the gene from each parent.

In a monohybrid cross between two heterozygous individuals, the alleles for a particular trait segregate during gamete formation, resulting in four possible combinations in the offspring:

- Homozygous dominant (AA)
- Heterozygous (Aa)
- Homozygous recessive (aa)

The phenotypic ratio of 3:1 is obtained when one homozygous dominant, two heterozygous, and one homozygous recessive individuals are produced in the offspring. This ratio demonstrates the segregation of alleles during gamete formation and their random combination during fertilization.

Thus, the phenotypic ratio of 3:1 proves the principle of segregation, which states that alleles for a particular trait segregate during gamete formation and are randomly combined during fertilization.