Mendelian inheritance: monohybrid and dihybrid crosses

What you’ll practice

Sharpen your ability to solve monohybrid and dihybrid crosses using Punnett squares, probability rules, and Mendel’s laws. You’ll translate word problems into allele notation, then predict genotype and phenotype ratios with confidence.

Each question has 4 options and there’s no timer, so you can slow down to check ratios or speed-run for exam-style practice. Before you start, choose how many questions you want to answer and select a difficulty level to match your current comfort.

Common pitfalls to avoid

Many mistakes come from mixing up genotype vs phenotype ratios, or forgetting to apply the product and sum rules correctly in multi-step probability. Another frequent slip is losing track of heterozygous parents or assuming traits assort together when the question implies independent assortment.

• Convert the prompt into clear allele symbols before building a Punnett square
• Double-check whether the question asks for genotype ratio, phenotype ratio, or a single probability
• Watch for testcross cues (unknown genotype crossed with homozygous recessive)
• For dihybrids, confirm you’re forming correct gametes (FOIL-style) before combining
• Reduce ratios properly and keep totals consistent (e.g., out of 4, 16, or 100%)

How the difficulty is balanced

Difficulty is mixed on purpose: you’ll see quick ratio recognition alongside problems that require multi-step reasoning, conditional probability, or interpreting crosses from outcomes. This blend helps you build speed on the basics while still practicing the kinds of twists that show up on biology exams.