- 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
