The human genome consists of 6 billion nucleotides in a double-stranded helical deoxyribonucleic acid (DNA) molecule. This genetic message codes for the building and operation of the human body. The message is written in an alphabet that uses only four letters: A, C, G, and T. Each of the letters represents one of the four bases which are the chemical building blocks of DNA: A— adenine, T— thymine, C — cytosine, and G — guanine. The nucleotides which spell out the genetic message are arrayed in a linear sequence in the double-stranded helical DNA molecule. The two strands of the DNA molecule are complementary copies of each other. The nucleotides on one strand pair with the complementary nucleotide on the other strand, as demonstrated in the top portion of Figure 1.1. A pairs with T; G pairs with C.
KeywordsHuman Genome Genetic Code Human Genome Project Chemical Building Block Genetic Message
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