Answer: B. nucleotide, gene, DNA molecule, chromosome. Reasoning:
- The smallest unit among the listed terms is the nucleotide, which combines a sugar, phosphate, and a base. A gene is a specific sequence of nucleotides within DNA. A DNA molecule is a long polymer made up of many nucleotides arranged into genes and other sequences. A chromosome is a structure that organizes and packages DNA into units that cells separate during division, containing one or more DNA molecules. Therefore, the correct size order from smallest to largest is nucleotide < gene < DNA molecule < chromosome.
