Practice question

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.