CHECKER BOARD (PUNNET'S SQUARE) METHOD

1.         If the genotypes of the parents are known, the genotypes of their offspring can be easily predicted with the help of a chart called Punnett square.

2.         It is named by an English geneticist Reginald Crundall Punnett (1875-1967) who first used this method in 1927.

3.         Its advantage lies in minimising the errors which can creep in when listing all possible combinations of gametes.

4.         Each box of the square represents an individual offspring.

5.         First the alleles in the gametes produced by the parents are determined.

6.         Now the boxes are filled in by combining the alleles of male and female gametes, working horizontally or vertically in each row.

7.         The allele combinations in the boxes show the possible genotypes of the F₁ generation. The ratios of the genotypes can then be worked out.