Final answer:
DNA is a double-stranded molecule, where each strand is made up of nucleotides, and it's organized into chromosomal structures within the nucleus of eukaryotic cells. The strands are held together by hydrogen bonds between nitrogenous bases, forming a double helix.
Step-by-step explanation:
The structure of DNA (deoxyribonucleic acid) is a double-stranded molecule that defines the genetic makeup of all living organisms. DNA molecules consist of two strands, a polymer of nucleotides, forming a shape known as a double helix. Each nucleotide in the DNA strand is made up of a nitrogenous base, a five-carbon sugar (deoxyribose), and a phosphate group. The alternating sugar and phosphate groups form the backbone of each DNA strand, while the nitrogenous bases (adenine, thymine, guanine, and cytosine) form hydrogen bonds with the bases on the opposite strand - adenine with thymine and guanine with cytosine - and bind the two strands together.
DNA is typically found in the nucleus of eukaryotic cells and is organized into structures called chromosomes. It is bound to proteins called histones forming nucleosomes, which further condense into chromatin and finally chromosomes. This structure facilitates the encoding, replication, and transfer of genetic information.
The correct answer to the student's question is the first option: 1) Double-stranded molecule bound to proteins in chromosomes in the nucleus.