Question

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine. Study the complete transcription unit given below and answer the following questions:

Identify coding strand and template strand of DNA in the transcription unit.

Hint:

RNA polymerase synthesizes the RNA strand using the template DNA strand, creating a complementary sequence that mirrors the coding strand (with uracil replacing thymine).

Answer 1

Identification of Coding and Template Strands in Transcription

Answer: Within a transcription unit:

• The template strand (or antisense strand) serves as the DNA template for RNA synthesis by RNA polymerase. Its sequence is complementary to the resulting RNA.
• The coding strand (or sense strand) possesses a sequence identical to the RNA transcript, with the exception of thymine (T) in DNA being replaced by uracil (U) in RNA.

Identification from Diagrams:

• The strand exhibiting the same orientation and nucleotide sequence as the mRNA (barring T/U differences) is designated the coding strand.
• The strand that is nucleotide-wise complementary to the mRNA is identified as the template strand.

Important Note:

In typical diagrammatic representations, the template strand is often depicted as running 3' to 5' (as this reflects the direction of RNA polymerase activity), while the coding strand is shown as 5' to 3'.