What is the typical phenotype ratio in a monohybrid cross?

In a monohybrid cross, typically involving two parents that are heterozygous for a single trait, the expected phenotype ratio observed in the offspring is 3:1. This ratio arises from the segregation of alleles during gamete formation, as governed by Mendel’s laws of inheritance.

When two heterozygous parents (for example, both are Tt, where "T" is dominant and "t" is recessive) are crossed, their gametes can combine to produce the following genotypes in a Punnett square:

1. TT (homozygous dominant)

2. Tt (heterozygous)

3. Tt (heterozygous)

4. tt (homozygous recessive)

This results in three offspring with the dominant phenotype (TT and Tt) and one offspring with the recessive phenotype (tt). Thus, the ratio of phenotypes is three showing the dominant trait to one showing the recessive trait, forming the classic 3:1 ratio.

Understanding this ratio is fundamental in genetics, as it reflects the predictable patterns of inheritance for single traits, which can be further applied in more complex genetic scenarios involving multiple traits.