1. Presence of genes as hereditary factors for the transmission of a trait from parents to offspring.
2. Genes exist in pairs, ie the same gene is found on both chromosomes of the homologous pair. The allele present on each chromosome may be the same, ie homozygous or different, ie heterozygous. For heterozygous condition, the dominant allele will be expressed.
3. Law of Segregation where the alleles of each gene will separate during gamete formation.
4. Each gamete will have one allele for a specific gene.
5. Random fertilisation where the gametes fuse randomly, regardless of the type of allele that they contain. This allows prediction of ratio of genotypes and phenotypes for genetic crosses.