Hierarchical Structure of Genetic Material

Steps:

• Chromosomes are thread-like structures in the nucleus made of DNA and proteins.
• DNA is a long molecule that forms the main component of chromosomes.
• Genes are specific segments of DNA that code for traits.
• A single chromosome contains thousands of genes, making it larger overall.

Why A is correct:

• By definition, a chromosome is a packaged structure containing one long DNA molecule with multiple genes, so it is physically larger than any single gene.

Why the others are wrong:

• B: Genes are subunits of chromosomes, not larger.
• C: Each chromosome consists of one DNA molecule, not the reverse.
• D: A gene is a continuous sequence on a single DNA molecule.

Final answer: A