Step 1: Understand the goal. DNA examination in forensics often involves separating DNA fragments based on their size.
Step 2: Evaluate the techniques.
(1) Electrophoresis: This is the standard technique for separating charged molecules like DNA and proteins. An electric field is applied to a gel matrix, and since DNA is negatively charged, it moves towards the positive electrode. Shorter fragments move faster and farther through the gel pores than longer fragments, resulting in separation by size.
(2) Gas chromatography (GC): This is used to separate volatile chemical compounds, not DNA.
(3) Atomic Absorption Spectroscopy (AAS): This is used to detect and quantify metallic elements.
(4) Nuclear Magnetic Resonance (NMR): This is used for determining the structure of chemical compounds.
Conclusion: Electrophoresis is the instrumental technique used to separate and examine DNA fragments.