In pea plants purple flowers are dominant to white flowers. If two white flowered plants are cross, what percentage of their offspring will be white flowered?
The correct answer and explanation is :
In pea plants, the allele for purple flowers (P) is dominant to the allele for white flowers (p). This means that a plant with at least one purple allele (PP or Pp) will have purple flowers, while only a plant with two recessive alleles (pp) will have white flowers.
When two white-flowered pea plants are crossed, both parents must have the genotype pp because white is recessive and can only be expressed when both alleles are recessive. The cross between these two plants is:
pp × pp
Each parent can only contribute a p allele, so the resulting offspring will all inherit one p from each parent, giving them a pp genotype.
Thus, all the offspring will be homozygous recessive (pp), which results in white flowers. Since the genotype pp leads to white flowers in pea plants, 100% of the offspring will have white flowers.
Punnett Square for the Cross:
To visualize the cross, we can use a Punnett square:
| p | p | |
|---|---|---|
| p | pp | pp |
| p | pp | pp |
As shown in the Punnett square, all of the possible offspring will inherit pp, meaning 100% of the offspring will have white flowers.
Summary:
The percentage of offspring with white flowers will be 100%. This is because both parent plants are homozygous recessive (pp), and all their offspring will inherit the recessive p allele from both parents, resulting in a genotype of pp, which leads to white flowers.