Final answer:
In eukaryotic cells, DNA is structured as a double helix, which is a shape formed by two strands of nucleotides twisting around each other. The DNA is organized into linear chromosomes and is tightly packed with histone proteins. Prokaryotic cells usually have a single circular chromosome with a simpler structure.
Step-by-step explanation:
The DNA within eukaryotic cells appears as a double helix, which resembles a twisted ladder or a spiral staircase. This structure is made up of two long strands of nucleotides that coil around each other. Each strand is made up of alternating deoxyribose sugars and phosphate groups, forming the backbone of the DNA molecule. Attached to the sugars are nitrogenous bases that pair specifically; adenine (A) with thymine (T) and guanine (G) with cytosine (C). These base pairs form the rungs of the 'ladder' and are held together by hydrogen bonds.
Eukaryotic DNA is organized into chromosomes, which are linear and consist of double-stranded DNA wrapped around proteins called histones. This allows the DNA to be tightly packaged within the nucleus of the cell. In contrast, most prokaryotic organisms have a single, circular chromosome consisting of a double-stranded DNA molecule without histones. During cell division, DNA replication occurs where the two strands of the double helix separate and become the template for the formation of two new complementary strands.