Correct Option: C. 1 : 3 Explanation of the Correct Answer The Mendelian law of segregation is one of the foundational principles of genetics, formulated by Gregor Mendel in the 19th century. This law states that during the formation of gametes (sperm and egg cells), the two alleles for a trait segregate from each other so that each gamete carries only one allele for each trait. When Mendel conducted his experiments with pea plants, he observed that when he crossed two purebred plants (one with dominant traits and one with recessive traits), the first generation (F1) all exhibited the dominant trait. However, when he allowed the F1 generation to self-pollinate, the recessive trait reappeared in the second generation (F2). In a typical monohybrid cross (where one trait is being studied), the phenotypic ratio of the offspring in the F2 generation is 3:1. This means that for every four offspring, three will display the dominant trait, and one will display the recessive trait. To summarize: - F1 Generation: All offspring show the dominant trait (e.g., if tall is dominant over short, all F1 plants are tall). - F2 Generation: When F1 plants are crossed, the offspring exhibit a phenotypic ratio of 3:1 (three tall plants to one short plant). This 3:1 ratio is derived from the combination of alleles during gamete formation and fertilization, which can be illustrated using a Punnett square. Why Other Options Are Incorrect

• Option A: 1 : 2
• This ratio does not represent any typical Mendelian inheritance pattern. It might suggest a scenario where two different traits are being considered, but it does not apply to the classic monohybrid cross that Mendel studied.
• Option B: 2 : 2
• This ratio simplifies to 1:1, which is characteristic of a test cross between a heterozygous and a homozygous recessive individual. It does not apply to the F2 generation of a monohybrid cross.
• Option D: 3 : 2
• This ratio is also not a standard outcome of Mendelian genetics. It does not correspond to any typical inheritance pattern observed in Mendel's experiments.

Summary of Key Concepts

• The Mendelian law of segregation explains how alleles separate during gamete formation.
• In a monohybrid cross, the F1 generation shows only the dominant trait.
• The F2 generation exhibits a phenotypic ratio of 3:1 (dominant to recessive).
• Understanding these ratios is crucial for predicting genetic outcomes in breeding and inheritance studies.

Revision Summary

• The Mendelian law of segregation states that alleles segregate during gamete formation.
• The F1 generation shows only the dominant trait.
• The F2 generation exhibits a 3:1 phenotypic ratio (dominant to recessive).
• Familiarity with Punnett squares can help visualize genetic crosses and outcomes.