Rank the following items in order from largest to smallest: cell, chromosome, gene, DNA, organism, nucleus.

In order from largest to smallest, we have: organism, cell, nucleus, DNA, chromosome, gene. The cell is the basic biological unit of the organism, so an organism is made up of one or more cells. Each of these cells contains a nucleus. Inside the nucleus of a cell is the cell's DNA. This DNA within the nucleus is divided into discrete units, called chromosomes. The number of chromosomes an organism has depends on its species. Humans have 46 (23 pairs of 2 chromosomes). Each chromosome is a single DNA molecule, which means that it is one long strand of DNA. A gene is a portion of DNA that codes for a specific protein. There are numerous genes contained in a chromosome. It is also important to know that the DNA contained in each cell of an organism is the same. This means that all the cells of an organism will have the same genes on the same set of chromosomes within their nuclei.

1. Organism - One basic characteristic of a living organism is that it must be made of one or more cells.
2. Cell- the cell is the most basic unit of life and encompasses smaller organelles (such as the nucleus in the eukaryotic cells).
3. Nucleus- the nucleus is found in eukaryotic cells and houses the genetic information (the DNA)
4. Chromosome- these structures contain the genetic information (DNA) . Human somatic cells contain 46 total chromosomes and human gametes contain 23.
5. Gene- Genes are segments of DNA that code for an organism's characteristics.
6. DNA- the nucleic acid that contains all of the information for synthesizing the necessary proteins for the organism.

The ranking of the given items from largest to smallest is as follows:
Organism > Cell > Nucleus > Chromosome > Gene > DNA
DNA is a molecule that can be thought of as the blueprint of life. In other words, it acts as a template which is replicated before cell division. It provides the information for building all the proteins within every living thing.
Gene is the basic functional and physical unit of heredity and is made up of DNA. Genes determine the traits and functions of a cell and are transferred from parent to daughter cells.
Chromosomes contain nucleic acids and proteins and they carry the genetic information in the form of genes.
The nucleus contains chromosomes. It is a membrane-bound structure and contains the hereditary information.
A cell is the smallest functional unit of life and contains nucleus and cytoplasm in a membrane-bound structure.
An organism is made up of a number of cells.
Hope this helps.