You are traveling in the Netherlands and overhear a tulip breeder describe a puzzling event. Tulips normally have two outer whorls of brightly colored petal-like organs, a third whorl of stamens, and an inner (fourth) whorl of carpels. However, the breeder found a recessive mutant in his field in which the outer two whorls were green and sepal-like, whereas the third and fourth whorls both contained carpels. What can you speculate about the nature of the gene that was mutated?

Key Concepts

Flower Structure and Whorls

Flowers are typically organized into whorls, which are layers of floral organs. The outer whorls consist of sepals, followed by petals, stamens, and carpels. Understanding this structure is crucial for analyzing mutations, as changes in specific whorls can indicate which genes are involved in flower development.

Dominance and Recessiveness in Genetics

In genetics, alleles can be dominant or recessive, influencing the expression of traits. A recessive mutation means that the trait only manifests when two copies of the mutated allele are present. This concept is essential for speculating about the nature of the mutated gene in the tulip, as the observed green sepals and carpel formation suggest a loss of function in the genes responsible for normal petal and stamen development.

Homeotic Genes and Floral Development

Homeotic genes are critical in determining the identity of floral organs during development. Mutations in these genes can lead to the transformation of one organ type into another, such as petals into sepals or stamens into carpels. The unusual floral structure observed in the tulip mutant suggests a possible mutation in homeotic genes, which could explain the presence of carpels in the third and fourth whorls.