Biological Hierarchy of Sizes

Steps:

• Gene is the smallest unit, a segment of DNA coding for traits.
• Chromosome is a larger structure made of coiled DNA containing many genes.
• Nucleus is the organelle enclosing chromosomes within the cell.
• Cell is the basic unit of life containing the nucleus.
• Tissue is a group of similar cells forming a functional unit, making it largest.

Why B is correct:

• It follows the precise size progression in cell biology: genes reside on chromosomes, which are inside the nucleus, within the cell, which composes tissues.

Why the others are wrong:

• A: Places chromosome before gene, but genes are subunits of chromosomes.
• C: Reverses gene and chromosome order; also puts tissue before cell, but cells form tissues.
• D: Places tissue before cell, ignoring that tissues consist of multiple cells.

Final answer: B