DNA sequencing is a laboratory process used to determine the exact order of nucleotides within a DNA molecule. It involves using special enzymes to break apart the DNA molecule and then using a specialized sequencing machine to read the sequence of the four nucleotides, which are adenine (A), thymine (T), guanine (G) and cytosine (C). The resulting sequence of nucleotides can then be compared to known sequences in order to identify differences in the DNA sequence and potentially diagnose genetic conditions or link individuals to specific traits.