Punnett Square: Cross Between White-Flowered and Purple-Flowered Pea Plants. The question marks (?) in the chart could be either B or b alleles. The Punnett square in Figure below shows this cross. The purple-flowered parent, on the other hand, could have either the BB or the Bb genotype.
Because the b allele is recessive, you know that the white-flowered parent must have the genotype bb. Suppose you have a parent plant with purple flowers and a parent plant with white flowers. Another example of the use of a Punnett square can be viewed at (5:40).Ī Punnett square can also be used to determine a missing genotype based on the other genotypes involved in a cross. Īn explanation of Punnett squares can be viewed at (25:16).
#Punnet square video how to#
At the link below, you can watch an animation in which Reginald Punnett, inventor of the Punnett square, explains the purpose of his invention and how to use it. The different possible combinations of alleles in their offspring are determined by filling in the cells of the Punnett square with the correct letters (alleles). The gametes produced by the male parent are at the top of the chart, and the gametes produced by the female parent are along the side. In this example, both parents are heterozygous for flowercolor ( Bb). An example of a Punnett square for pea plants is shown in Figure below. Predicting the possible genotypes and phenotypes from a genetic cross is often aided by a Punnett square.Ī Punnett square is a chart that allows you to easily determine the expected percentage of different genotypes in the offspring of two parents. Though the above fruit may not result, it would be nice to scientifically predict what would result. What do you get when you cross an apple and an orange?
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