This says billions, medical science i am behind, but pairs.......b/c some of the chemicals always pair with another..............but only 4...........so if u knew the sequence of that.......us, a human or a plant or a t rex.......and had all 4 bases/acids, whatever they exactly are.........u could bake yourself up a velociraptor...

The human genome is roughly 3.1 to 3.2 billion base pairs long, with a complete, gap-free sequence now available. Each base pair is one of four chemical "letters" of DNA (G, A, T, or C), and if stretched out, the DNA from a single human cell would be about 2 meters (6 feet) long. 

Key details about the human genome's length:

• Number of base pairs:

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  It's approximately 3.1 billion to 3.2 billion base pairs in length, depending on the reference assembly. 
• The reference genome:

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  The human reference genome represents one copy of each chromosome and is not the entire genome of a single individual. 
DNA molecule:
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A single copy of the human genome, when stretched out, is about 2 meters (6 feet) long