Question

Two pure-breeding phlox plants were crossed, one with dark-blue flowers and the other with pink flowers. The F 1 generation all had dark-blue flowers. When the F 1 were crossed with each other, the F 2 generation consisted of 176 plants: 101 with dark-blue flowers, 33 with light-blue flowers, 30 with red flowers, and 10 with pink flowers.

How is flower color controlled in phlox?
- one gene with two co-dominant alleles
-one gene with four alleles
-two genes with dominant epistasis
- two genes whose alleles interact additively

Answer 1

The phlox plants experiment indicates a complex inheritance pattern beyond a simple Mendelian monohybrid cross. Unlike Mendel's 3:1 ratio observed in pea plants, the observed flower colors in the F2 phlox generation suggest multiple alleles or gene interactions.

Step-by-step explanation:

In the phlox plants experiment involving two pure-breeding phlox plants, one with dark-blue flowers and the other with pink flowers, the F1 generation showed dominant dark-blue flowers. This suggests that the dark-blue flower color is a dominant trait over pink flowers. When the F1 generation phlox plants were crossed with each other, the resulting F2 generation displayed a variety of flower colors including dark-blue, light-blue, red, and pink.

This variation in the F2 generation is indicative of multiple alleles or gene interactions contributing to the flower color phenotype. Mendel's experiments with pea plants, for example, demonstrated that one trait could mask the presence of another, leading to a 3:1 ratio in the second generation (F2). Three of every four plants exhibited the dominant phenotype, while one exhibited the recessive phenotype.

However, the phlox experiment suggests a more complex inheritance pattern, potentially involving more than one gene, since the observed ratios do not align neatly with a simple monohybrid cross as seen in Mendel's pea plant experiments.