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  • Reginald C. Punnett came up with the Punnett square.
  • It is a square diagram which is used to predict the genotypes of a particular cross.
  • During a breeding experiment, possible outcomes of offspring are studied using  Punnett squares.

Consider these examples of a Punnett squares:

Example 1 : Eye colour

 

  • Parent 1 - Homozygous Dominant Brown colour eyes ( BB ).
    The 2 alleles B and B are written on one side of the square.
  • Parent 2 - Homozygous Recessive Blue colour eyes ( bb ).
    The 2 alleles b and b are written on the other side of the square.
  • Corresponding alleles are written in each box, one from each parent to find possible combinations .
  • The offsprings in the F 1 generation have all Heterozygous Brown colour eyes ( Bb )

Example 2: Pod colour of pea plant

 

  • Plant 1 - Heterozygous Dominant Green pod ( Gg ).
    The 2 alleles G and g are written on one side of the square.
  • Plant 2 - Homozygous Recessive Yellow pod ( gg ).
    The 2 alleles g and g are written on the other side of the square.
  • Corresponding alleles are written in each box, one from each parent to find possible combinations.
  • The offsprings have all Heterozygous Green pods ( Gg ) and Homozygous Recessive Yellow pods ( gg ) in the ratio 1:1

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo