Year 12 / Genetics and heredity
Separate. Recombine. Inherit.
Meiosis produces haploid gametes. Homologous chromosomes separate, so each gamete receives one allele for a given gene. Independent assortment and crossing over generate variation, though linked genes may not assort independently.
A Punnett square lists possible gamete combinations. For a simple dominant–recessive trait with two heterozygous parents, expected genotype proportions are 1 AA : 2 Aa : 1 aa. These are probabilities, not exact family counts.
Punnett square
Explore: Choose parental genotypes and read the offspring genotype grid.
Cross two Aa parents for a complete-dominance trait.
- Each parent can contribute A or a.
- One of four equally likely combinations is aa.
Assumed knowledge
Fractions and chromosomes.
Learning checkpoints & source
YOUR LEARNING CHECKPOINT- Model allele segregation in meiosis.
- Predict simple genetic cross outcomes.
READY TO TRY IT?