DNA undergoes transcription to form a complementary mRNA strand. The process of copying genetic information from the template strand of DNA into RNA is called transcription. The strand of DNA with polarity 3′→5′ serves as the template strand. The transcription starts from the 3′ end of the DNA and a new molecule of mRNA with 5′→3′ polarity is formed alongside the template strand. Since transcription results in the formation of mRNA, the complementary base to adenine would be uracil and not thymine. Thus the correct sequence of the complementary mRNA strand would be 5′ - UACGUACGUACG −3′