Human DNA is 99.9% identical from person to person. Although 0.1% difference doesn't sound like a lot, it actually represents millions of different locations within the genome where variation can occur, equating to a breathtakingly large number of potentially unique DNA sequences. The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people.
Zygote Fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm).
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