How could you compare DNA to a city?

DNA is the genetic blueprint for an organism.  In humans, a DNA strand contains 3 billion base pairs.  That long DNA strand is divided into more manageable sections.  Those sections are called chromosomes.  I'll use humans again.  Humans have 46 chromosomes.  A chromosome contains genes.  A gene is a section of a chromosome, which is the same thing as saying that a gene is a section of DNA.  A gene is then composed of a...

DNA is the genetic blueprint for an organism.  In humans, a DNA strand contains 3 billion base pairs.  That long DNA strand is divided into more manageable sections.  Those sections are called chromosomes.  I'll use humans again.  Humans have 46 chromosomes.  A chromosome contains genes.  A gene is a section of a chromosome, which is the same thing as saying that a gene is a section of DNA.  A gene is then composed of a certain number of base pairs.  The number of base pairs depends on the gene; however, the organization of a single base pair is the same.  A base pair is composed of two nucleotide units that have been "attached" to each other with the nitrogen base.  A nucleotide is composed of a deoxyribose, a phosphate, and 1 of 4 possible bases.  Those bases are Adenine (A), Thymine (T), Guanine (G) and Cytosine (C).  A always pairs with T, and C always pairs with G.  The order of the nitrogen bases functions like a code that determines how our body grows and functions.  

It is possible to compare the structure and organization of DNA to a city.  Each nitrogen base could be compared to an individual home on a street.  A bunch of homes in a row would then be similar to a gene.  Not all of the homes on a street are identical homes (different bases), and not all streets have the same number of homes or types of homes (different genes).  The entire series of streets in a given neighborhood would then be a single chromosome.  Cities have many different neighborhoods just like DNA has different chromosomes.  All of the streets/neighborhoods together in a single city would then be similar to all of the chromosomes of a single cell's DNA.