The Difference between a template and a coding strand is primarily based on two characteristics: directional polarity and function. The two distinct strands of double-stranded DNA are the template strand and the coding strand, with the former functioning as a base to transcribe mRNA and the latter determining the correct base sequence of the mRNA.

Directional Polarity: The template strand moves from the 3’end to the 5’end, while the coding strand moves in the opposite direction, from the 5’end to the 3’end.

Base Sequence: The base sequence of the template strand is complementary to both the coding and mRNA strands. In contrast, the base sequence of the coding strand is identical to that of the new mRNA strand with the exception of the substitution of uracil for thymine.

The primary focus of this session will be on the main differences between the template and coding strand, as well as the comparison chart. In addition, you will learn the definitions and examples of each term.

Difference Between Template and Coding Strand (Coding Strand vs. Template Strand )

• Definition:
  • Template Strand: The non-coding DNA segment of a specific gene.
  • Coding Strand: Acts as the non-template segment during transcription.
• Alternate Names:
  • Template Strand: Often termed as the antisense strand or minus strand.
  • Coding Strand: Commonly referred to as the sense strand, non-template strand, or plus strand.
• Base Sequence:
  • Template Strand: The RNA synthesized is complementary to the template strand.
  • Coding Strand: The RNA sequence mirrors the coding strand of DNA, with the exception of uracil replacing thymine.
• Polarity:
  • Template Strand: Exhibits a 5’ to 3’ orientation.
  • Coding Strand: Oriented in a 3’ to 5’ direction.
• Complementary Nucleotide Sequence:
  • Template Strand: Absent.
  • Coding Strand: Present.
• Genetic Coding:
  • Template Strand: Encompasses anti-codons.
  • Coding Strand: Contains codons.
• Transcription into mRNA:
  • Template Strand: Undergoes transcription into mRNA.
  • Coding Strand: Does not participate in mRNA transcription.
• Hydrogen Bond Formation:
  • Template Strand: During transcription, ephemeral hydrogen bonds form between the template strand and the nascent mRNA.
  • Coding Strand: No hydrogen bonds form between the coding strand and the synthesizing mRNA during transcription.
• Functional Role:
  • Template Strand: Serves as the blueprint for mRNA formation, guiding its synthesis.
  • Coding Strand: Determines the accurate nucleotide sequence for the resultant mRNA.

Comparison Chart Between Coding Strand vs. Template Strand

In the intricate realm of DNA transcription, two primary strands play pivotal roles: the template strand and the coding strand. These strands, while closely related, possess distinct characteristics and functions. Herein, we delineate the differences between these two strands based on various parameters:

Parameter	Template Strand	Coding Strand
Definition	The template strand is the non-coding DNA segment of a specific gene.	The coding strand acts as the non-template segment during transcription.
Alternate Names	Often termed as the antisense strand or minus strand.	Commonly referred to as the sense strand, non-template strand, or plus strand.
Base Sequence	The RNA synthesized is complementary to the template strand.	The RNA sequence mirrors the coding strand of DNA, with the exception of uracil replacing thymine.
Polarity	Exhibits a 5’ to 3’ orientation.	Oriented in a 3’ to 5’ direction.
Complementary Nucleotide Sequence	Absent	Present
Genetic Coding	Encompasses anti-codons.	Contains codons.
Transcription into mRNA	Undergoes transcription into mRNA.	Does not participate in mRNA transcription.
Hydrogen Bond Formation	During transcription, ephemeral hydrogen bonds form between the template strand and the nascent mRNA.	No hydrogen bonds form between the coding strand and the synthesizing mRNA during transcription.
Functional Role	The template strand, also known as the antisense or minus strand, is instrumental in RNA synthesis. It serves as the blueprint for mRNA formation, guiding its synthesis.	The coding strand, alternatively termed the sense or plus strand, is paramount in determining the accurate nucleotide sequence for mRNA during transcription. Its sequence is akin to the resultant mRNA, barring the thymine-uracil substitution. This strand is dubbed the sense strand due to its role in dictating the protein-coding sequence.

In essence, while the template strand provides the necessary template for RNA synthesis, the coding strand ensures the accurate sequence for the resultant mRNA. Both strands, with their unique attributes and functions, are indispensable for the intricate process of transcription and the broader realm of genetics.

What is Template Strand?

• The template strand, a fundamental component of DNA, is pivotal in the intricate process of mRNA synthesis, facilitated by the principle of complementary base pairing. This strand possesses a directionality of 3′ to 5′, which is antithetical to both the coding strand and the resultant mRNA.
• Notably, the template strand is devoid of coding capabilities, earning it designations such as the non-coding, anticoding, or antisense strand. Its nucleotide sequences are complementary to those in the transcribed mRNA and the coding strand.
• During the transcription process, the RNA polymerase enzyme meticulously reads the template strand, orchestrating the commencement of transcription. Unlike the coding strand, the template strand meticulously guides the mRNA’s formation through complementary base pairing, ensuring the mRNA sequence mirrors that of the coding strand.
• In the context of transcription, the template strand’s primary function is to serve as a blueprint for mRNA synthesis. The enzyme RNA polymerase, instrumental in transcribing genes into mRNAs, appends nucleotides in a 5’ to 3’ direction to the nascent mRNA strand.
• Given this, the template strand’s 3’ to 5’ orientation is imperative, allowing for the addition of complementary nucleotides to the burgeoning mRNA strand in the 5’ to 3’ direction. Consequently, within the double-stranded DNA, the template strand is accountable for the amino acid sequence of the resultant polynucleotide chain. Its counterpart in the double-stranded DNA is termed the non-template strand.
• Intriguingly, the template strand encompasses a series of anti-codons, which are nucleotide triplets analogous to those in individual tRNAs. These anti-codons are complementary to the codons present in the non-template or coding strand.
• During synthesis, the mRNA transiently binds to the template strand, forming hydrogen bonds with its complementary nucleotides. A noteworthy deviation occurs when RNA polymerase incorporates uracil into the mRNA strand as a counterpart to adenine in the template strand, rather than thymine.
• To elucidate further, the template strand is the non-coding segment of a specific gene’s DNA. Often referred to as the anti-sense or positive strand, this strand is exposed by the enzyme DNA helicase during transcription. RNA polymerase reads this strand from the 3′ to 5′ direction.
• The template strand’s anticodon shares nucleotide sequences identical to tRNA. Serving as the transcriptional starting point for mRNA, the template strand ensures the accurate base sequence selection for the mRNA.

Example of Template Strand

Let’s consider an example of a template strand to understand its function in mRNA synthesis. Suppose we have a template strand with the gene sequence 5′-ATCGCGTA-3′. In this case, RNA polymerase (RNAP) will initially bind to the promoter region of the DNA sequence, initiating the process of transcription. The template strand will then be transcribed to form the primary mRNA transcript.

Since mRNA is formed with complementary base sequences to the template strand, the resulting mRNA sequence will be 3′-UAGCGCAU-5′. Each nucleotide in the mRNA sequence is complementary to the corresponding nucleotide in the template strand.

In this example, the template strand provides the necessary information for the synthesis of mRNA. The base pairing rules dictate that adenine (A) in the template strand corresponds to uracil (U) in the mRNA, thymine (T) corresponds to adenine (A), cytosine (C) corresponds to guanine (G), and guanine (G) corresponds to cytosine (C).

The resulting mRNA sequence, 3′-UAGCGCAU-5′, carries the genetic information transcribed from the template strand. This mRNA can then undergo further processing and modifications, such as the addition of a poly-A tail and removal of introns, to become a mature mRNA molecule ready for translation into a protein.

This example illustrates how the template strand serves as a template during transcription, guiding the synthesis of an mRNA molecule with complementary base sequences to ensure accurate transfer of genetic information.

What is Coding Strand?

• The coding strand, an integral component of DNA, is characterized by its sequence similarity to mRNA, with a singular distinction: the substitution of thymine (T) in DNA with uracil (U) in mRNA. This strand exhibits a 5′ to 3′ directionality, which is antipodal to the template strand. Intriguingly, the coding strand encompasses codons, tri-nucleotide groupings that dictate specific amino acids during the intricate process of protein synthesis.
• Contrary to the template strand, the coding strand does not directly engage in mRNA formation during transcription. Nonetheless, its significance is underscored by the congruence of its sequence with that of the mRNA. As the template strand is meticulously read to craft mRNA, the coding strand ensures the resultant mRNA molecule faithfully replicates the coding strand’s sequence.
• Often referred to as the non-template strand in the context of transcription, the coding strand’s nucleotide bases align with those in the mRNA sequence, barring thymine. Instead, uracil, a nitrogenous base, supplants thymine in mRNA.
• Given its pivotal role in determining the RNA sequence, which subsequently encodes a specific amino acid sequence of a protein, the coding strand is also aptly termed the sense strand. This strand, from its 5′ end to its 3′ end, is read directionally. Embedded within the coding strand are codons, nucleotide triplets that signify particular amino acids in the resultant polypeptide chain.
• In the realm of transcription, the coding strand, which also exhibits a 5’ to 3’ orientation, is designated as the non-template strand. Due to its directionality, the coding strand is precluded from serving as the template during transcription.
• A salient feature of the coding strand is its possession of codons, nucleotide triplets that demarcate distinct amino acids in the polypeptide chain. Collectively, these codons constitute the genetic code, a universal attribute prevalent across nearly all extant life forms.
• A noteworthy distinction between the template and coding strands is illustrated in Figure 2, which depicts the role of the coding strand in transcription. The coding strand’s nucleotide sequence mirrors that of the primary mRNA transcript. Consequently, bioinformatic tools, such as GLIMMER and GeneMark, which are instrumental in gene identification within specific DNA sequences, rely heavily on the coding sequence for gene prediction.
• Owing to the coding strand’s sequence parallels with mRNA, unique mRNA sequences, including the start codon, stop codon, and the open reading frame, are discernible within the coding sequence. These attributes, coupled with promoter sequences, empower bioinformatics tools to predict genes utilizing the Ab initio method.

Example of Coding Strand

Let’s consider an example of a coding strand based on the template strand sequence 5′-ATCGCGTA-3′. According to the Watson and Crick model, the coding strand will produce complementary base pairs relative to the template strand.

In this example, the sense strand’s base sequence will be 3′-TAGCGCAT-5′. Each nucleotide in the sense strand is complementary to the corresponding nucleotide in the template strand. Adenine (A) in the template strand pairs with thymine (T) in the sense strand, cytosine (C) pairs with guanine (G), and guanine (G) pairs with cytosine (C).

During transcription, RNA polymerase (RNAP) binds to the promoter region of the DNA sequence and initiates the process of transcription. The template strand is then transcribed to form the primary transcript, which has a base sequence of 3′-UAGCGCAU-5′.

In this example, the coding strand provides the complementary sequence to the template strand, which ultimately determines the sequence of the transcribed mRNA. The primary transcript, with the base sequence 3′-UAGCGCAU-5′, carries the genetic information transcribed from the template strand and is further processed to become a mature mRNA molecule.

This example illustrates how the coding strand pairs with the template strand to generate a complementary mRNA sequence during transcription. The coding strand plays a crucial role in protein synthesis by providing the necessary genetic code in the form of codons that determine the sequence of amino acids in the resulting protein.

Key Differences Between Template and Coding Strand

1. Alternative Names:
   • Template strand: Minus strand, antisense strand, non-coding strand.
   • Coding strand: Plus strand, sense strand, non-template strand.
2. Function:
   • Template strand: It serves as the base for RNA synthesis during transcription.
   • Coding strand: It determines the correct nucleotide base sequence of the RNA strand.
3. Directional Polarity:
   • Template strand: It runs in the 3′-5′ direction.
   • Coding strand: It runs in the opposite direction, 5′-3′.
4. Reading by RNA Polymerase:
   • Template strand: RNA polymerase reads the template strand from the 3′-5′ direction and synthesizes the RNA transcript by adding complementary nucleotides relative to the template.
   • Coding strand: RNA polymerase does not directly read the coding strand.
5. Nucleotide Base Sequence:
   • Template strand: Its base sequence (3′-5′) is complementary to the base sequence of both the coding strand and the resulting mRNA transcript (5′-3′).
   • Coding strand: Its base sequence is the same as the newly formed mRNA, except thymine (T) is replaced by uracil (U) in mRNA.
6. Genetic Coding:
   • Template strand: It contains tRNA anticodons, which carry triplet nucleotide sequences complementary to the anticodon sequence of tRNA.
   • Coding strand: It includes codons, which are triplet nucleotide sequences that code for specific amino acids to form a peptide chain.
7. Formation of Hydrogen Bond:
   • Template strand: During transcription, a temporary hydrogen bond forms between the template strand and the newly synthesized mRNA.
   • Coding strand: No such hydrogen bond forms between the coding strand and the mRNA.

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