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: In a transcription unit: 

• The template strand (also called antisense strand) is the DNA strand that is used by RNA polymerase to synthesize RNA. It is complementary to the RNA sequence.
• The coding strand (also called sense strand) is the DNA strand that has the same sequence as the RNA transcript (except it has thymine (T) instead of uracil (U)).

How to Identify from the Diagram:

• The strand with the same direction and sequence as the mRNA (except T in place of U) is the coding strand.
• The strand that is complementary to the mRNA is the template strand.

Note:

Typically, in diagrams, the template strand is labeled 3' to 5' (because RNA polymerase reads in this direction), and the coding strand is 5' to 3'.