A cross is the mating of two organisms. In a monohybrid cross only one pair of contrasting characteristics is studied (Human Perspectives: 2012). For a particular characteristic, the genes for an individual are, represented by two letters, one for the gene that originated from the female parent and one for the gene that originated from the male parent. If the gene is dominant then it is displayed as a capital letter, whereas if it is recessive then a lower case letter is used. For the garden pea experiment, the green pod colour is dominant to yellow, so the gene for the green pod is represented with a G and the recessive gene for yellow pod colour is a lower case g. For pure breeding plants of green pod colour the symbols would be GG and with pure breeding plants of yellow pod colour would be gg. Hybrids with one of each would be represented as Gg. The alternative forms of the gene for seed colour, in this case are called alleles. For a pair of contrasting characteristics the two alleles may occur in either combination: GG, gg, Gg. In two of the three genotypes, the alleles are the same, this means they are homozygous, whereas the hybrid, Gg, with one of each allele, is termed heterozygous. The physical appearance, or what the seeds look like is called the phenotype.