Question

What are the different terms used to describe the two strands of DNA involved in transcription?

Short answer

Template strand and coding strand.

Step-by-step solution

Identify the Two DNA Strands

Understand that DNA is double-stranded, consisting of two complementary strands. Each strand has a role in transcription.

Define the Template Strand

The template strand, also known as the non-coding strand, is the strand of DNA that is used as a template by RNA polymerase to synthesize messenger RNA (mRNA).

Define the Coding Strand

The coding strand, also known as the non-template strand, is the DNA strand that has a sequence identical to the mRNA (with thymine replaced by uracil). This strand is not used directly for RNA synthesis.

Key concepts

template strand

The template strand of DNA, also known as the non-coding strand or antisense strand, plays a crucial role in the process of transcription. This strand serves as the guide or template for synthesizing messenger RNA (mRNA).

The RNA polymerase enzyme reads the template strand and uses its sequence to build a complementary mRNA strand. Since DNA strands are complementary, the sequence of the template strand is used to determine the order of nucleotides in the mRNA, but with one difference: thymine (T) in DNA is replaced by uracil (U) in RNA.

In summary:

• The template strand is the DNA strand that is copied into RNA during transcription.
• RNA polymerase reads this strand to make mRNA.
• Thymine (T) is replaced by uracil (U) in the newly formed RNA.

coding strand

The coding strand, often referred to as the non-template strand or sense strand, is the DNA strand whose base sequence corresponds with the base sequence of the mRNA transcript produced (though typically, thymine (T) in DNA is replaced by uracil (U) in RNA).

This strand is called the coding strand because its sequence is identical to the mRNA sequence (with T replaced by U). It means that if you look at the mRNA sequence and the coding strand of DNA, they will be very similar except that RNA has uracil (U) instead of thymine (T).

In summary:

• The coding strand’s sequence matches the mRNA sequence (with T replaced by U).
• This strand is not directly used by RNA polymerase to make mRNA.
• It’s the template strand that is used for synthesizing RNA.

RNA polymerase

RNA polymerase is an essential enzyme in the process of transcription. It’s responsible for synthesizing RNA from the DNA template strand.

This enzyme performs several important functions during transcription:

• Binding to DNA: RNA polymerase binds to a specific region of DNA known as the promoter.
• Unwinding DNA: The enzyme then unwinds the double-helix structure of DNA to access the template strand.
• RNA Synthesis: RNA polymerase reads the template strand and builds a complementary RNA strand by adding nucleotides one by one.
• Termination: Once the whole gene is transcribed, RNA polymerase releases the newly made RNA and detaches from the DNA.

In essence, RNA polymerase is critical for converting the genetic information encoded in a DNA strand into a movable, readable form (mRNA) that the cell can use to produce proteins.