Punnett Squares

Mendel proposed that you inherit a gene either from your mother, or from your father. But not a mixture of both. In this video we are going to look at monohybrid crosses using Punnett squares. A monohybrid cross is the study of the inheritance of one characteristic - such as the pea-pod colour. A Punnett square is a diagram that is used to predict the outcome of a particular cross. It is used by biologists to determine the probability of an offspring having a particular genotype. The genotype represents the genes of the organism, and is shown by two letters. A capital letter represents the dominant form of a gene (or allele), and a lowercase letter represents the recessive form of the gene. In punnett squares, we start with an empty grid and write down the genotypes of both parents. Cross the parents genotypes to represent the possible offspring genotypes. Punnett squares show the probability of offspring genotypes. However, these are just probabilities. They are the expected results. The actual results may be different.