How do bands from linear fragments differ in appearance from plasmid bands?

How do bands from linear fragments differ in appearance from plasmid bands?

• A. Linear fragments have trailing edges.
• B. Plasmid bands have trailing edges.
• C. Both forms show identical band shapes.
• D. Neither form shows trailing edges.

Answer: (A)

Band shape on a gel reflects the DNA’s form. Linear fragments have ends and can suffer slight end-fraying or slight variation in end states as they migrate, which creates a tail or trailing edge behind the main band. Plasmid DNA, being circular, can adopt compact conformations (like supercoiled or relaxed circular) that migrate as tighter, more discrete bands with little or no tail. So linear fragments show trailing edges, while plasmid bands tend to be cleaner and more compact without that tail.

Band shape on a gel reflects the DNA’s form. Linear fragments have ends and can suffer slight end-fraying or slight variation in end states as they migrate, which creates a tail or trailing edge behind the main band. Plasmid DNA, being circular, can adopt compact conformations (like supercoiled or relaxed circular) that migrate as tighter, more discrete bands with little or no tail. So linear fragments show trailing edges, while plasmid bands tend to be cleaner and more compact without that tail.