Difference Between Replication and Transcription

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Replication

DNA replication can be described as the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. This is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, like the parent cell.

The basis of the replication process is the fact that each strand of DNA can serve as a template for duplication. The process initiates at specific points, called origin of reapplication points, where the DNA double helix is unwound. A short segment of RNA, called a primer, is then synthesised and acts as a starting point for new DNA synthesis. The enzyme DNA polymerase next begins replicating the DNA by matching bases to the original strand. Once DNA synthesis is completed, the RNA primers are replaced with DNA. If there are any gaps between the newly synthesised DNA segments, they are sealed together with enzymes.

DNA replication is a crucial process; therefore, to ensure that mistakes, or mutations, are not introduced, the cell proofreads the newly synthesised DNA. Once the cellular DNA is replicated, the cell can divide into two daughter cells, which would have identical copies of the original DNA.

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Transcription

Transcription can be explained as the process by which the genetic information contained within DNA is re-written into a messenger RNA (mRNA) with the help of  RNA polymerase. This mRNA then exits the cell nucleus, where it provides the basis for the translation of DNA. 


The Stages of Transcription

The process of transcription can be divided into 3 main stages: 

Initiation

The process is catalysed by the enzyme RNA polymerase. It attaches to a DNA and moves along with it until it recognises a promoter sequence, which indicates the starting point of transcription. There may be many promoter sequences in a DNA molecule. Transcription factors are proteins that control the rate of transcription and also bind to the promoter sequences with RNA polymerase. 

Once bound to the promoter sequence, RNA polymerase unwinds a portion of the DNA double helix, exposing the bases on each of the two DNA strands.


Elongation

One DNA strand known as the template strand is read in a 3′ to 5′ direction and so provides the template for the new mRNA molecule. The other DNA strand is termed as the coding strand because the base sequence of the new mRNA is identical to it, except for the replacement of thiamine bases with uracil.

Incoming ribonucleotides are used by RNA polymerase to form the mRNA strand. It does this using complementary base pairing (A to U, T to A, C to G and G to C). RNA polymerase then catalyses the formation of phosphodiester bonds between adjacent ribonucleotides. Bases can only be added to the 3′ (three-prime) end, so the strand elongates in a 5’ to 3’ direction.


Termination

Elongation will continue until the RNA polymerase encounters a stop sequence. At this point, transcription terminates and the RNA polymerase releases the DNA template.

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In this article, we will learn both similarities and differences between replication and transcription.


Difference Between Dna Replication and Transcription

DNA replication and transcription are two complex biological processes and they have several differences between them. These differences between transcription and DNA replication are mentioned below:

Replication vs Transcription

Character

DNA replication

Transcription

Definition

It is the process of making new copies of DNA.

It is the process by which DNA is copied and transcribed to an RNA.

Significance

It is important for the regulation of the growth and division of cells.

It is the method of regulating gene expression.

Transfer of genetic information

Genetic information transfers from DNA to DNA.

The genetic information transfers from DNA to RNA.

Occurs during

The S phase of the cell cycle.

Transcription takes place in the G1 and G2 phases of the cell cycle.

Motive 

Takes place in preparation for cell division.

It takes place in preparation for protein translation.

Involved in 

The process is involved in cell division

The process is involved in gene expression.

Raw materials

The raw materials utilised are dATP, dGTP, dCTP and dTTP.

ATP, GTP, CTP and GTP are the raw materials in this process.

Template 

Both DNA strands act as templates.

A single DNA strand acts as a template.

Primers

The process requires an RNA primer to start replication.

No primers are needed to start this process.

Enzymes

The enzymes that are required are DNA polymerase, DNA helicase.

RNA polymerase, transcriptase.

Unwinding and splitting

Involves the unwinding and splitting of the DNA molecule.

Involves the unwinding and splitting of the genes that are to be transcribed.

Base pairing 

Adenine pairs with Thymine

Adenine pairs with Uracil

Copying of template

The complete template is copied.

Only a part of the DNA template that codes for required genes are transcribed or copied.

Product

Two daughter molecules of DNA.

mRNA, rRNA, non-coding RNA and tRNA

Strands in product

Double-stranded DNA

Single-stranded RNA

Post-formation

Joining and Okazaki fragments.

RNA editing.

Processing

The DNA molecules that are produced are not needed for processing.

The primary RNA  transcript molecule needs processing to acquire the final form.

Bond

The new DNA molecules remain together by hydrogen bonds to the template DNA strand

THE transcribed RNA strand separates from its DNA template strand.

Rate of production

The rate of replication is typically 20 times faster than transcription and six or more replication forks may be present at the same time on the chromosome.

Comparatively slower.

FAQ (Frequently Asked Questions)

1. What Are the Similarities Between Replication and Transcription?

Alongside differences, there are also some similarities between DNA replication and transcription. Both replication and transcription involve binding complementary nucleic acids to DNA, which yields a new strand of either DNA or RNA. 

The processes can lead to errors if an incorrect nucleotide is incorporated. An error in either transcription or replication can cause a change in the gene. This occurs by either changing the DNA sequence in one of the daughter cells leading to transcription of the incorrect mRNA sequence or by causing the mRNA to incorporate an incorrect base pair that results in the wrong protein sequence being translated.

2. Write the Comparison Between Replication and Transcription.

Please have a look at the main part of this topic and the first question of the FAQ section.

3. What Are the Steps of DNA Replication?

The four steps of DNA replication are:

  1. Replication fork formation

  2. Primer binding

  3. Elongation

  4. Termination

In eukaryotes, it takes place in the nucleus of the cell whilst in prokaryotes, it takes place in the cytoplasm of the cell.