Make a sketch of a simplified flower with all four organs, and indicate how the pattern of expression for just two genes (e.g., 'D' and 'E') could, hypothetically, regulate the development of each organ.
Consider that what's important is whether a gene is on or off and that a structure can be specified when neither gene is expressed.

Verified step by step guidance

1. Begin by sketching a simplified flower diagram. Label the four main organs: sepals, petals, stamens, and carpels. These are the typical parts of a flower that are involved in reproduction and protection.
2. Introduce the concept of gene expression regulation. In this hypothetical scenario, we have two genes, 'D' and 'E'. The expression of these genes can be either 'on' (expressed) or 'off' (not expressed), and this will influence the development of the flower's organs.
3. Consider the pattern of gene expression for each organ. For example, if gene 'D' is expressed and gene 'E' is not, this might lead to the development of sepals. Conversely, if gene 'E' is expressed and gene 'D' is not, petals might develop.
4. Explore the scenario where both genes 'D' and 'E' are expressed. This could hypothetically lead to the development of stamens, as the combination of both gene expressions might specify this organ.
5. Finally, consider the situation where neither gene 'D' nor gene 'E' is expressed. In this case, the development of carpels might occur, as the absence of both gene expressions could specify this organ. This demonstrates how gene expression patterns can regulate organ development in a flower.

Key Concepts

Flower Structure and Organs

A typical flower consists of four main organs: sepals, petals, stamens, and carpels. These organs are arranged in concentric circles called whorls. Sepals protect the flower bud, petals attract pollinators, stamens produce pollen, and carpels contain the ovary. Understanding these structures is crucial for visualizing how gene expression affects flower development.

Gene Expression Regulation

Gene expression regulation involves turning genes on or off to control cellular functions. In the context of flower development, specific genes must be activated or deactivated to form different floral organs. The hypothetical genes 'D' and 'E' could represent transcription factors that, when expressed, initiate the development of particular flower parts, while their absence allows for the formation of other structures.

ABC Model of Flower Development

The ABC model explains how combinations of gene expression determine the identity of floral organs. Although the question uses 'D' and 'E' genes, the principle remains that specific gene combinations lead to the development of sepals, petals, stamens, and carpels. This model helps in understanding how turning genes on or off can result in the formation of different flower parts, even when using hypothetical genes.