Those DNA molecules that have the most copies of a given sequence will reanneal fastest in solution because there is a higher probability of encounter between complementary sequences. Hence more complex single-copy sequences take the longest to reanneal. The probability of a long sequence encountering its complementary sequence in a mixture of sequences in a given time is small because of its lower concentration when compared with other multiple-copy sequences. This situation can be modeled by assuming second-order kinetics (Chap. 5) for reannealing, because the rate of association is proportional to the concentration of each strand. The parameter of greatest interest is C0t½ that is estimated by regression of an exponential function onto the experimental data. This is the time taken for 50% of renaturation to occur.
