A plant can produce either purple flowers or white flowers. What is the probability of purple-flowered offspring if two plants that are heterozygous for purple flowers are crossed? 1:4 2:4 3:4 4:4
The correct answer and explanation is:
The correct answer is 3:4.
Explanation:
In this case, we are dealing with a genetic cross between two plants that are both heterozygous for purple flowers. The trait for flower color is likely governed by a Mendelian pattern of inheritance, where purple flower color is dominant over white flower color. Let P represent the dominant allele for purple flowers and p represent the recessive allele for white flowers.
The two plants are heterozygous, meaning their genotypes are Pp.
When these two plants are crossed, the possible offspring genotypes can be predicted using a Punnett square.
Punnett Square Setup:
| P | p | |
|---|---|---|
| P | PP | Pp |
| p | Pp | pp |
From the Punnett square, we can see the following potential genotypes of the offspring:
- PP (homozygous dominant): 1 out of 4
- Pp (heterozygous): 2 out of 4
- pp (homozygous recessive): 1 out of 4
Since P (the purple flower allele) is dominant, both PP and Pp will result in purple flowers. Only the pp genotype will result in white flowers.
Thus, 3 out of 4 offspring (PP, Pp, Pp) will have purple flowers, and 1 out of 4 (pp) will have white flowers.
Therefore, the probability of offspring with purple flowers is 3:4.
This pattern of inheritance follows Mendel’s laws of inheritance, where dominant and recessive alleles segregate during gamete formation, and the genotypes combine randomly during fertilization. The key here is recognizing that the dominant purple allele can produce the purple flower phenotype even in the heterozygous condition.