What is the phenotypic effect of inserting a Ds element into the maize C gene? How do Ds and Ac produce maize kernels that are mostly yellow with purple spots?

Key Concepts

Transposable Elements

Transposable elements, or 'jumping genes,' are DNA sequences that can change their position within the genome. In maize, the Dissociation (Ds) element is a type of transposable element that can disrupt gene function when inserted into a gene, such as the C gene, which is responsible for color in kernels. This insertion can lead to phenotypic changes, such as altered pigmentation.

C Gene and Kernel Color

The C gene in maize is crucial for the production of anthocyanin pigments, which contribute to the color of the kernels. When the Ds element inserts into the C gene, it can disrupt its function, leading to a loss of pigment production. This results in kernels that may exhibit a yellow color due to the absence of anthocyanin, with purple spots appearing where the gene is still functional.

Activator (Ac) and Dissociation (Ds) Interaction

The Ac (Activator) element is another transposable element that can promote the movement of Ds elements within the genome. When Ac is present, it can facilitate the excision of Ds from the C gene, potentially restoring its function in some cells. This interaction can create a mosaic pattern in the kernels, leading to a phenotype where most kernels are yellow, but some exhibit purple spots due to the reactivation of the C gene in specific areas.