In pea plants, purple flowers are dominant over white flowers. The phenotype ratio of purple to white flowers in a population of five plants is 4:1. How many plants have white flowers?
1
2
4
5
The correct answer and explanation is:
The correct answer is 1.
In this case, the phenotype ratio of purple to white flowers is given as 4:1. This means that for every 4 plants with purple flowers, there is 1 plant with white flowers.
The total number of plants is 5. The ratio of 4:1 means that for every group of 5 plants, 4 of them will have purple flowers, and 1 will have white flowers.
Therefore, in a population of 5 plants, 1 plant will have white flowers and the remaining 4 will have purple flowers.
This ratio comes from the genetic inheritance of flower color in pea plants. The purple flower color is dominant over white, so a plant with at least one dominant allele for purple (P) will have purple flowers. Only plants that are homozygous recessive (pp) will have white flowers.
For this scenario to hold, you would expect 1 out of every 5 plants to inherit two recessive alleles (pp) for the white flower trait, and the other 4 to inherit at least one dominant allele (P) for purple flowers.
This pattern can be explained using a Punnett square, which shows that if two heterozygous (Pp) pea plants are crossed, the expected ratio of offspring with purple flowers (PP or Pp) to those with white flowers (pp) will be 3:1. In a population of 5 plants, you would expect 1 plant to be white (pp) and 4 to be purple (PP or Pp).
Thus, the answer is 1 plant with white flowers.