Anuj M. answered 04/11/20
Ph.D. in Molecular & Medical Genetics; 4+ years teaching experience
The template, or non-coding (or anti-sense), strand of DNA and the coding (or sense) strand of DNA are complementary and anti-parallel. The template strand is what is "read" during transcription by the RNA polymerase in the 3' to 5' direction to make a complementary RNA that is in the 5' to 3' direction. Since the coding strand of DNA and the RNA are both complementary to the template strand of DNA, the coding (or sense) strand tells you the code (or gives you a sense) of the RNA, with the exception that all T's in the coding strand become U's in the RNA, since RNA uses uracil bases instead of thymine bases (with a few exceptions in tRNA, in which uradine nucleotides are converted to thymidine nucleotides). Hence, if you are given the template (or non-coding) strand sequence of DNA = 5'-AGT-3', you would first re-write it 3' to 5' and then write the coding strand under it.
3'-TGA-5'
5'-ACT-3'
The corresponding codon found in the mRNA would be the same sequence as the coding strand, except replacing all T with U: 5'-ACU-3'
However, if the _coding_ strand sequence is given as 5'-AGT-3', then the RNA sequence is simply 5'-AGU-3'
Emma D.
Hi Kathryn,
Here is how mRNA is created: coding DNA gets transcribed to template DNA, then template DNA gets transcribed to mRNA.
It is important to remember that 5' ends get "transcribed" to 3' ends. So the template DNA 5'AGT3' is transcribed to the mRNA 3'UCA5'. But since it is customary to write codons from 5'-end to 3'-end, the mRNA codon is actually ACU.
coding DNA: 5' ACT 3'
template DNA: 3' TGA 5'
mRNA: 5' ACU 3'
Hope this helps!
12/05/12