Method for synthesizing DNA strand

A primer extension reaction method for structure-independent amplification of DNA comprising:

• preparing a reaction mixture containing sample DNA having CG rich repeats, primers, one or multiple enzymes capable of synthesizing a nucleic acid strand complementary to the sample DNA, a mixture of dNTPs, and a buffer,
• denaturing DNA in the reaction mixture at a denaturing temperature in a denaturation step,
• annealing the primers at an annealing temperature in an annealing step,
• extending the annealed primers in an extension step to obtain amplified DNA, wherein in the extension step includes raising the temperature from the annealing temperature to a first lower extension temperature in the range of 70-90° C., then fluctuating the temperature up to a second higher extension temperature in the range of 80-95° C. and back down to the first lower extension temperature for a plurality of fluctuation cycles to destabilize the secondary structures in the DNA to allow the extension, and wherein the difference between the first extension temperature and the second extension temperature is in the range of 3-10° C.