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What is DNA?

What is DNA?

Every living thing on Earth shares the most fundamental structure of life: deoxyribonucleic acid, or DNA. Packed inside virtually every cell, DNA carries the genetic information needed to build and maintain an organism. Whenever living things reproduce, that DNA instruction book is passed on to the next generation.


A single human eye has hundreds of millions of cells--microscopic units of life. The cell's nucleus contains nearly all of its DNA.


Chromosomes are bundles of DNA that carry genetic information from parents to offspring. Humans have 23 pairs of chromosomes, inheriting half of each pair from each parent.

DNA Base Pairs

DNA is made up of two very long strands twisted together. DNA carries information encoded in a long series of four chemicals: adenine, thymine, cytosine and guanine, or A, T, C and G.


© AMNH / Denis Finnin

Liver cell cross-section, revealing DNA


Characteristics ranging from hair color to health are influenced by particular segments of DNA. Together these segments, called genes, control how our bodies look and function.


In a multi-step process, genes tell our bodies how to develop and function. First, the gene is used as a template to make a messenger RNA (mRNA). 


© AMNH Exhibitions


Next, mRNA carries the gene's information outside the nucleus to the ribosome, or protein factory.


Finally, the ribosome translates the genetic code and builds a protein. Each protein does a specific task in the body, such as growing bone or fighting infections.

Where is DNA?

Cells are the tiny building blocks that make up all living things. And inside each of the 100 trillion cells that make up the human body is DNA.

Look at this human liver cell. Can you find the two different parts of the cell that house its DNA? Most of the DNA is in the nucleus. The rest is found in the thousands of tiny mitochondria, the cell's energy generators.

In a real cell, the DNA stays packed inside--it doesn't spring out and grow larger, as it does in this model!

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