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A DNA molecule looks a bit like a twisted ladder—a shape that scientists call the “double helix.”
The DNA from all living organisms, including plants, fungi, animals, and bacteria is made of the same material, arranged in this double-helix shape.
Let’s take a closer look…
The DNA Ladder’s Structure
The “rails” or vertical sides of the ladder-like DNA are made of long chains of sugar and phosphate molecules, which alternate as they hook up; a sugar, then a phosphate, etc.
The “rungs” in the ladder connect to the sugar molecules along the rails. These rungs are made of four chemical compounds called “bases” that bond in pairs: adenine (A) with thymine (T), and guanine (G) with cytosine (C).
 Climbing the Ladder
If you were to climb the DNA ladder, you would discover that the sequence of the rungs—the order of the base pairs—changes step by step. This sequence or “code” is what guides a cell’s development and behavior.
So, while the DNA of all living things is made of the same six components (sugar, phosphate and A, T, C and G), it is the sequence of these components that creates the differences between organisms and the great diversity of life on Earth.
One of DNA’s primary roles is to store and transmit this sequence or code within a cell.
Continue to How Does DNA Work? >>
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