What is the expected phenotype ratio of a monohybrid cross?

• A. 1:2
• B. 2:1
• C. 3:1
• D. 1:1

Answer: (C)

In a monohybrid cross, where two individuals differing in a single trait are bred, the expected phenotype ratio is 3:1. This scenario typically involves one dominant allele and one recessive allele.

When crossing two heterozygous individuals (e.g., Aa x Aa), the potential gametes formed are A and a. The combination of these gametes in the offspring results in four possible genotypes: AA, Aa, Aa, and aa.

From this combination, the phenotypes can be categorized based on the dominance of the alleles. The dominant phenotype (from both AA and Aa) will appear three times, while the recessive phenotype (from aa) will appear once. Thus, the resulting ratio of the dominant phenotype to the recessive phenotype is 3:1, which reflects the expected outcome of a typical monohybrid cross.