What is the chemical structure that contains the blueprint for an organism?

The double helix is the correct answer because it refers to the specific three-dimensional structure of DNA, which contains the genetic blueprint for an organism. Each strand of DNA in the double helix is composed of a sequence of nucleotides, which form the building blocks of genes. These genes carry the instructions required for the development, functioning, growth, and reproduction of all living organisms.

The iconic double helix structure, first described by Watson and Crick, illustrates how the two strands of DNA are wrapped around each other, providing stability and allowing for the precise replication and transcription necessary for passing genetic information from one generation to the next.

In contrast, single-stranded structures, such as RNA, are not the primary carriers of an organism's genetic blueprint, although they play crucial roles in synthesizing proteins from the DNA sequence. Circular DNA is typically found in prokaryotic organisms and certain organelles, but it does not represent the common structural form associated with the genetic blueprint of eukaryotic organisms.