Transcription: Scientists may one day replace defective genes with normal ones by removing a bit of DNA from a cell and adding an enzyme. The enzyme helps to create a hybrid or recombinant DNA. Every organism has millions of strands of DNA in each cell. Each strand is in the shape of a double helix and is made up of nucleotides thymine, adenine, cytosine, and guanine. By unwinding and bonding with free-floating nucleotides, a new double helix is created and the process begins again.
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