DNA sequencing is the process of determining the exact order of nucleotides (A, T, C, G) in a DNA molecule. This is crucial for understanding genetic information, diagnosing diseases, conducting biological research and generating DNA profiles for legal cases.

These are the 5 main steps, needed for DNA sequencing:

1. Sample Preparation
   The DNA is extracted from cells and purified to remove proteins and other contaminants. This step ensures that only the DNA is used for sequencing.

2. Fragmentation and Preparation
   The DNA is broken into smaller fragments by ultrasound or enzymes to allow further steps. Adapters (short DNA sequences) are added to both ends of these fragments to help them attach to the DNA polymerase and allow for amplification.

3. Amplification
   During a process called PCR (Polymerase Chain Reaction) the enzyme DNA polymerase copies the DNA fragments many times. This creates enough copies of each fragment to be detected and sequenced.

4. Sequencing Reaction
   The actual sequencing takes place in the sequencer. This involves reading the order of nucleotides in each fragment, often using fluorescent dyes that emit light signals corresponding to each nucleotide. The sequencer reads those lights, giving a string of data.

5. Data Analysis
   The raw sequencing data is processed to assemble the nucleotide sequences of the fragments. The fragments are then aligned and combined to reconstruct the original DNA sequence. Errors are corrected, and the final sequence is analyzed for biological insights.

Each of these steps is critical to ensure accurate and reliable sequencing results.