A DNA strand has the base sequence of ACGT. What is the complementary RNA base pairing that would occur during transcription? A) ACGA B) UGCA C) TCCA D) AGCT E) TTCC
The correct answer is choice B) UGCA.
Transcription is the system that produces a complementary RNA sequence from a strand of DNA. Transcription is initiated when RNA polymerase connects to the DNA template strand in an area called the promoter region and starts stringing together a new complementary RNA strand in the 3' to 5' direction. The resulting new strand of mRNA has complementary base pairs to the original DNA template. DNA has four nitrogenous bases: (A) adenine, (T) thymine, (C) cytosine, and (G) guanine. RNA contains three of these bases - (A),(C), and (G) but not (T). Uracil (U) is found in its place and complements adenine (A) instead. Therefore if the original DNA template strand read ACGT, the RNA strand will attach uracil to adenine so the complementary RNA strand will read UGCA.