Genetic crosses are deliberate mating of two individuals with specific characteristics. The two individuals to be mated have to be of the same species.
To illustrate the genetic cross, genetic diagrams are used to show the possible ways where alleles are segregated in gametes and how gametes containing different types of alleles randomly fuse (Mendel's Law of Segregation and Random fertilisation) to form offsprings of different genotypes. Genetic cross allows prediction of expected ratios of genotypes and phenotypes only for a large number of offsprings (progeny).
Format of genetic diagrams
Genetic diagrams should have the following headings.
Parental phenotypes
Parental genotypes
Gametes
F1 generation genotypes
F1 generation phenotypes
Phenotypic ratio