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Biology
Mendelian inheritance — From parents to offspring
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Trace alleles from pea parents through gametes to offspring, then compare theoretical probabilities with random samples.
n = 0
About the cross
Two F1 plants of the same genotype give the same distribution as F1 self-fertilisation in this model. Mendel allowed F1 plants to self-fertilise.
Dominance describes expression in a heterozygote, not strength, superiority or a higher chance of transmission.
n = 0
0%50%100%
Yellow
Theoretical probability: 3/4 (75%)
Observed: No sample yet
Green
Theoretical probability: 1/4 (25%)
Observed: No sample yet
Dashed marker: theory. Filled bar: sample frequency, which can differ.
Genotype distribution
| Genotype | Theoretical probability | Observed |
|---|---|---|
| YY | 1/4 | — |
| Yy | 1/2 | — |
| yy | 1/4 | — |
Each parent contributes one allele at each locus.
Model notes
- This model uses diploid pea plants and complete dominance: Y/y represents seed colour, R/r seed shape. Each gamete carries one allele at each locus being studied.
- The two loci are on different chromosome pairs and assort independently. Linkage, mutation, selection, unequal viability and environmental effects are excluded.
- Each offspring is an independent random fertilisation. Finite samples can differ from theory; increasing sample size does not guarantee a smaller deviation at every step.
- Pollen donor and recipient are roles. Allele-bearing symbols represent gametes, not pollen grains. Offspring seeds show the phenotype after development, not the immediate appearance of a zygote.
- The diagram is not to biological scale or real time and does not depict one meiotic event. Do not use it to infer human traits or disease.