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  • In a plant, tallness is dominant over dwarfness, and red flower is dominant over white. Starting with the parents work out a dihybrid cross. What is the standard dihybrid ratio?

In a plant, tallness is dominant over dwarfness, and red flower is dominant over white. Starting with the parents work out a dihybrid cross. What is the standard dihybrid ratio? Do you think the values would deviate if the two genes in question are interacting with each other?

Answers (1)

The cross between a dwarf plant with white flowers (ttrr) and tall plant with red flowers (TTRR) is depicted by the Punnett Square shown below:

Plants of the F1 generation will produce red flowers and will be tall. When they are permitted to self-pollinate, F2 generation’s phenotype can be depicted by following Punnett Square.

Here, the ratio is 9:3:3:1, which is the standard dihybrid ratio, also shown as:

  • Tall plant red flower = 9
  • Tall plant white flower = 3
  • Dwarf plant red flower = 3
  • Dwarf plant white flower = 1

This ratio stands true only when the contrasting characters have their genes on distinct chromosomes. This is because of the fact that there will be interaction if the characters are on the same chromosome.

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infoexpert23

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