Final answer:
The Ac transposase gene contains no introns and is composed of a single open reading frame (ORF), indicating the answer to the question is option 'd'. Unlike many eukaryotic genes, the Ac transposase gene is an exception, as it does not have any intervening non-coding sequences between exons.
Step-by-step explanation:
The question pertains to the structure of the Ac transposase gene, which is a gene that is capable of independent transposition in the maize Ac/Ds system. Transposable elements or transposons are segments of DNA that can move around to different positions within the genome of a single cell. The Ac element has a gene that codes for an enzyme called transposase, which is required for the cutting and reinsertion of the DNA segment within the genome.
As for the structure of the Ac transposase gene itself, which is comprised of exons and introns, the correct answer to the question of how many exons and introns it contains is 'd There are no introns in the Ac gene'. This means that the single open reading frame (ORF) of the Ac transposase gene does not have introns interrupting it.
In general, many eukaryotic genes consist of exons and introns, with introns being non-coding sequences that are removed during RNA processing. However, this is not the case for the Ac transposase gene; it is an exception to this general rule in eukaryotic gene structure.