Explain fully, in your own words, why the temperature during PCR goes through cycles of 94C, 50C, 72C.

The DNA polymerase used in PCR reaction usually can tolerate high temperature (94degree celcius), the temperature necessary to separate two complementary strands of DNA in a test tube.

If PCR goes through 72degree celcius, which is the temperature optimum for taq polymerase. It starts the extension process where taq polymerase will work away from the primer provided and generated a new DNA strand.

If PCR goes through 50degree celcius, it is annealing temperature. It is related to the melting temperature of the primers and must be determined for each primer pair used in PCR.