define dideoxysequencing
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Dideoxysequencing, also known as Sanger sequencing, is a method for determining the order of DNA sequences. It involves the use of modified nucleotides called dideoxynucleotides (ddNTPs) that lack a hydroxyl group on the 3' carbon of the sugar molecule. These ddNTPs are incorporated into a growing DNA strand during polymerization, but cause chain termination as they lack the necessary hydroxyl group for the next nucleotide to attach. By using fluorescently-labeled or radiolabeled ddNTPs, the terminated fragments can be separated by size through gel electrophoresis and the sequence can be determined by analyzing the order of the fragments produced. This method played a key role in the Human Genome Project and continues to be used for DNA sequencing in research and medical applications.