Final answer:
DNA is the genetic blueprint that contains the instructions for building and operating an organism, encoded in sequences of four nucleotide bases. It resides in the nucleus, is replicated during cell division, and directs the creation of proteins, which are vital for cell structure and function.
Step-by-step explanation:
DNA, or Deoxyribonucleic Acid, is often referred to as the "blueprint" or "code of life" because it contains the unique genetic instructions essential for the development and functioning of all living organisms. The analogy of a blueprint is apt because, just as a blueprint contains the detailed plan of a building, DNA houses the instructions for making all the proteins that a cell needs to operate and dictates the organism's traits. These instructions are a sequence of four nucleotide bases - adenine (A), cytosine (C), guanine (G), and thymine (T) - whose order determines the genetic information.
Within a cell, DNA resides in the nucleus where it is organized into chromosomes. Each cell (excluding germ cells) holds a complete copy of an organism's DNA. When cells divide, DNA is replicated so new cells receive the same set of instructions.
This replication ensures that the genetic material is passed from parents to offspring, making it the foundation for hereditary traits. Any given sequence of DNA is known as a gene, and genes specify the creation of messenger RNA (mRNA), and subsequently, the formation of proteins through a process called gene expression. Proteins are not only crucial for the structure of a cell but are involved in virtually all cell functions, including as enzymes to facilitate biochemical reactions, affirming the central role of DNA within cellular life.