What does symmetric cutting at 2 sites in circular DNA result in?
In circular DNA, two restriction sites placed diametrically opposite divide the circle into two equal halves. After complete digestion, two fragments of identical molecular weight are produced. During agarose gel electrophoresis, migration rate depends on size, not sequence content. Fragments of same length co-migrate, overlapping as a single intensely stained band despite being two distinct physical pieces. Asymmetric placement would give two bands of different sizes. Recognizing symmetry explains why band number may appear less than fragment number and intensity doubles.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.