BRIEF NOTE ON COMPLEMENTARY GENES

•     Bateson and Punnett crossed two different white flowered varieties of sweet pea and obtained
  an F1 progeny of red flowered plants. 
• On self pollination the F1 plants gave an F2 progeny of 9red and 7 white flowered plants.
•  Single crosses between the red flowered variety and the twodifferent white flowered varieties showed that the gene for red colour was dominant over the gene for each of the two white varieties.
  The cross between the two white varieties can be explained by assuming two genes for
  red colour which must be present together, i.e., must act in a complementary way to each
  other.
•  Thus each gene independently contributes something different but essential for synthesis
  of red pigment.
•  If one of the two genes for red colour is absent, the result is a white flower. 
• The inheritance of the colour of aleurone layer in corn also demonstrates interaction of
  complementary genes. 
• The outermost layers of endosperm in the maturing corn kernels become
  modified into a specialised aleurone tissue, so named because the cells have rich deposits of
  aleurone grains.
•  In corn the aleurone layer is coloured due to anthocyanin pigments in the
  cells, and is controlled by complementary effect of two genes
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