Consider a short piece of single stranded DNA trying to bind to a much longer strand of single stranded DNA. There are three places on the long strand that perfectly match the sequence of the short strand. When the short strand finds these spots, it binds with a strong binding energy ES. However, the short strand can also bind weakly to places where the sequence does not match. There are 104 weak binding locations with a binding energy EW. At body temperature (37° C) kBT = 4.28×10-21J (hint: you can use this number but it is much, much easier if you don't) Calculate PS/PW, the ratio of the probability that the short strand is bound to one of the three strong sites to the probability that it is in one on the weak sites. Use ES = -10kBT and EW = -2kBT.

 

Calculate Ps/Pw, the ratio of the probability that the short strand is bound to one of the three strong sites to the probability that it is in one on the weak sites. Use Es = -10kBT and Ew = -2kBT. Number 10 U Strong sites, Short strand Weak sites Strong binding Weak binding