Genetic crosses in flowering plants use parental genotypes, gametes and offspring ratios to infer inheritance patterns in inheritance problems in inheritance problems.
Coverage 2014–2023 · Updated 16 Jul 2026
A flowering-plant cross transfers pollen carrying male gametes to a stigma so fertilization can combine known parental alleles.
| Generation | What to do and record |
|---|---|
| P | Choose parents with known contrasting traits and control which pollen reaches the stigma |
| F1 | Grow the first filial offspring and record their phenotype(s) |
| F2 | Cross or self-pollinate suitable F1 plants, then compare observed offspring with a Punnett-grid prediction |
Pollen is the practical source of male gametes; female gametes are inside ovules in the ovary. Pea flowers can self-pollinate, which helps maintain pure-breeding lines and produce controlled F2 generations.
Cross two pure-breeding parents with contrasting traits, record a uniform F1, then self-pollinate the F1 and compare the F2 counts with the predicted genotype and phenotype ratios.
A Punnett grid predicts probabilities, not exact counts. Controlled crosses are used in crop and ornamental breeding, but pollination is transfer of pollen, not fertilization itself.
This objective is assessed through structured response, commonly using Identify.
Identify
Build the answer around this relationship: Parental genotypes determine the gametes available in a cross.
Representative question
L. purpureus can have purple or white flowers. Two pure-breeding varieties were crossed: HA 4 with white flowers and GL 424 with purple flowers. All of the plants had purple flowers. The plants were self-pollinated to produce an generation. There were 97 plants with purple flowers and 38 plants with white flowers in the generation.
Using a Punnett grid, explain the results of this cross.
Core D3.2 is secure when the student can move from allele rules into predictions and evidence: gametes form genotypes, genotypes can produce phenotypes, different dominance patterns need different notation, and pedigrees or plots require evidence-based interpretation.
Core inheritance exam questions reward disciplined reasoning. First identify the inheritance rule, then write the correct notation or evidence, then state the phenotype, ratio, or conclusion. This prevents the common mistake of writing definitions without solving the genetic problem.
