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WAEC Biology 2012 Question 54

Question 54

Mendelian Inheritance

Two plants with red flowers were back crossed, which of the following results indicate that the plants are heterozygous red flowers, where red flowers are dominant?

  1. A.75% red and 25% white
  2. B.50% red and 50% white
  3. C.100% white
  4. D.100% red
Show the answer and explanation

Answer: A (75% red and 25% white)

Explanation

Crossing two heterozygous red plants (Rr × Rr) gives 3 red : 1 white, i.e. 75% red and 25% white; white offspring prove both parents carry r.