Inheritance and Genetics: Explain the offspring genotypes and phenotypes when two heterozygous individuals reproduce.

This is a common and important genetics question to study. First let's pick out the key terminology. Genotype is the genetic code that gives rise to a physical characteristic - a phenotype. At GCSE, all the genotypes will involve only two alleles which can either be dominant or recessive. Heterozygous means an individual carries both a dominant allele and a recessive allele - for this scenario we will denote them as T (dominant) and t (recessive.) So a heterozygous individual has the genotype Tt.When Tt crosses with another Tt the likely offspring can be calculated using a 'Punnet Square' (see whiteboard.) As we can see, the outcomes are TT, Tt, Tt and tt. ALWAYS remember to go back and see exactly what the question asked for. Here, we were asked for the different genotypes AND phenotypes, so make sure to write them out fully with percentages i.e. 50% Heterozygous offspring (express dominant phenotype), 25% Homozygous Dominant offspring (express dominant phenotype) and 25% Homozygous Recessive offspring (express recessive phenotype.)