Genetics and Inheritance: Predict Pea Plant Traits
Understand that each parent passes on one allele per trait, that a dominant allele masks a recessive one, and that the Punnett square gives the expected ratios which real samples approach as numbers grow.
Before you try
What if two tall pea plants had a short child? How could that possibly happen?
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What happened?
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Only one gene with two versions is modelled. Most real traits come from many genes working together, and the environment matters too.
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Try these ideas
- Cross Tt with Tt and check the 3 to 1 phenotype ratio.
- Grow 20 offspring, then 200 more, and watch the observed percentage settle.
- Find the parent pair that gives half tall and half short plants.
Why it works
Every pea plant carries two alleles for each trait, one from each parent. A dominant allele, written as a capital letter, hides a recessive one, so a plant shows the recessive form only when it has two recessive alleles. That is why Tt and TT both look tall. The alleles a plant carries are its genotype and what you can see is its phenotype, and the two are not the same thing.
The Punnett square sets one parent’s possible gametes along the top and the other’s down the side, giving four equally likely combinations. In this simulator you pick the parents, read the expected ratios, then grow samples of offspring and compare the observed counts. Small samples wander; large ones close in on the prediction. Many real traits involve many genes plus the environment, so this one-gene model does not explain them.
Check your understanding
Question 1 of 4
Two tall pea plants, both Tt, are crossed. What fraction of offspring are expected to be short?
A plant with the genotype Tt looks what?
What is the difference between genotype and phenotype?
Does this simple dominant and recessive model explain human height?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Look at family photos and discuss which features seem to run in the family.
- Ask why Mendel chose pea plants for his experiments.
- Toss two coins many times and link the outcomes to a Punnett square.