Monohybrid Ratio
The monohybrid ratio is the expected ratio of traits or genotypes when only one character is studied in a cross.
Practice This ConceptMain explanation
Teacher explanation
In a monohybrid cross, only one pair of contrasting traits is considered, such as tall and short stem height. When two heterozygous parents are crossed, the offspring show a standard pattern: the genotype ratio is 1:2:1 and the phenotype ratio is 3:1. This chapter often asks students to identify or use these ratios in simple crosses.
Example
If Tt is crossed with Tt, the offspring can be TT, Tt, Tt, or tt. The phenotypic result is three tall plants and one short plant.
Simple analogy
One trait, one cross, 1:2:1 and 3:1.
Common confusion
Students often mix genotype ratio with phenotype ratio. They also forget that the 3:1 result is for visible traits, not for gene combinations.
Exam tip
For a monohybrid cross of two heterozygous parents, remember 1:2:1 for genotype and 3:1 for phenotype.
Answer writing and exam use
1-mark use
Write the exact meaning of monohybrid ratio in one clean line.
2-mark use
Define monohybrid ratio and add one example or condition.
3-mark use
Explain monohybrid ratio, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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