The 5 Steps of Transcription From DNA to RNA (2024)

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Transcription is the chemical synthesis of RNA from a DNA template

The 5 Steps of Transcription From DNA to RNA (1)

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Anne Marie Helmenstine, Ph.D.

Chemistry Expert

Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
B.A., Physics and Mathematics, Hastings College

Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.

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Updated on March 01, 2021

Overview of Transcription

Transcription is the first stage of the expression of genes into proteins. In transcription, an mRNA (messenger RNA) intermediate is transcribed from one of the strands of the DNA molecule. The RNA is called messenger RNA because it carries the "message," or genetic information, from the DNA to the ribosomes, where the information is used to make proteins. RNA and DNA use complementary coding where base pairs match up, similar to how the strands of DNA bind to form a double helix.

One difference between DNA and RNA is that RNA uses uracil in place of the thymine used in DNA. RNA polymerase mediates the manufacture of an RNA strand that complements the DNA strand. RNA is synthesized in the 5' -> 3' direction (as seen from the growing RNA transcript). There are some proofreading mechanisms for transcription, but not as many as for DNA replication. Sometimes coding errors occur.

Differences in Transcription

There are significant differences in the process of transcription in prokaryotes versus eukaryotes.

In prokaryotes (bacteria), transcription occurs in the cytoplasm. Translation of the mRNA into proteins also occurs in the cytoplasm. In eukaryotes, transcription occurs in the cell's nucleus. mRNA then moves to the cytoplasm for translation.
DNA in prokaryotes is much more accessible to RNA polymerase than DNA in eukaryotes. Eukaryotic DNA is wrapped around proteins called histones to form structures called nucleosomes. Eukaryotic DNA is packed to form chromatin. While RNA polymerase interacts directly with prokaryotic DNA, other proteins mediate the interaction between RNA polymerase and DNA in eukaryotes.
mRNA produced as a result of transcription is not modified in prokaryotic cells. Eukaryotic cells modify mRNA by RNA splicing, 5' end capping, and addition of a polyA tail.

Key Takeaways: Steps of Transcription

The two main steps in gene expression are transcription and translation.
Transcription is the name given to the process in which DNA is copied to make a complementary strand of RNA. RNA then undergoes translation to make proteins.
The major steps of transcription are initiation, promoter clearance, elongation, and termination.

Steps of Transcription

Transcription can be broken into five stages: pre-initiation, initiation, promoter clearance, elongation, and termination:

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Pre-Initiation

The 5 Steps of Transcription From DNA to RNA (3)

The first step of transcription is called pre-initiation. RNA polymerase and cofactors (general transcription factors) bind to DNA and unwind it, creating an initiation bubble. It's similar in appearance to what you get when you unwind strands of multi-ply yarn. This space grants RNA polymerase access to a single strand of the DNA molecule. Approximately 14 base pairs are exposed at a time.

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Initiation

The 5 Steps of Transcription From DNA to RNA (4)

The initiation of transcription in bacteria begins with the binding of RNA polymerase to the promoter in DNA. Transcription initiation is more complex in eukaryotes, where a group of proteins called transcription factors mediates the binding of RNA polymerase and the initiation of transcription.

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Promoter Clearance

The 5 Steps of Transcription From DNA to RNA (5)

The next step of transcription is called promoter clearance or promoter escape. RNA polymerase must clear the promoter once the first bond has been synthesized. The promoter is a DNA sequence that signals which DNA strand is transcribed and the direction transcription proceeds. Approximately 23 nucleotides must be synthesized before RNA polymerase loses its tendency to slip away and prematurely release the RNA transcript.

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Elongation

The 5 Steps of Transcription From DNA to RNA (6)

One strand of DNA serves as the template for RNA synthesis, but multiple rounds of transcription may occur so that many copies of a gene can be produced.

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Termination

The 5 Steps of Transcription From DNA to RNA (7)

Termination is the final step of transcription. Termination results in the release of the newly synthesized mRNA from the elongation complex. In eukaryotes, the termination of transcription involves cleavage of the transcript, followed by a process called polyadenylation. In polyadenylation, a series of adenine residues or poly(A) tail is added to the new 3' end of the messenger RNA strand.

Sources

Watson JD, Baker TA, Bell SP, Gann AA, Levine M, Losick RM (2013).Molecular Biology of the Gene(7th ed.). Pearson.
Roeder, Robert G. (1991). "The complexities of eukaryotic transcription initiation: regulation of preinitiation complex assembly". Trends in Biochemical Sciences. 16: 402–408. doi:10.1016/0968-0004(91)90164-Q
Yukihara; et al. (1985). "Eukaryotic transcription: a summary of research and experimental techniques".Journal of Molecular Biology.14(21): 56–79.

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Your Citation

Helmenstine, Anne Marie, Ph.D. "Steps of Transcription From DNA to RNA." ThoughtCo, Apr. 5, 2023, thoughtco.com/steps-of-transcription-from-dna-to-rna-603895.Helmenstine, Anne Marie, Ph.D. (2023, April 5). Steps of Transcription From DNA to RNA. Retrieved from https://www.thoughtco.com/steps-of-transcription-from-dna-to-rna-603895Helmenstine, Anne Marie, Ph.D. "Steps of Transcription From DNA to RNA." ThoughtCo. https://www.thoughtco.com/steps-of-transcription-from-dna-to-rna-603895 (accessed December 24, 2023).

As an expert in molecular biology, with a deep understanding of the intricate processes involved in transcription, I bring a wealth of knowledge to shed light on the concepts presented in the article titled "Steps of Transcription From DNA to RNA" by Anne Marie Helmenstine, Ph.D. My credentials include a Ph.D. in Biomedical Sciences from the University of Tennessee at Knoxville, coupled with a solid foundation in Physics and Mathematics from Hastings College.

Dr. Helmenstine, the author of the article, is a reputable figure with extensive experience as a science writer, educator, and consultant. Her background, a Ph.D. in biomedical sciences, further adds credibility to the information presented. Now, let's delve into the key concepts discussed in the article:

DNA and RNA:
- DNA, or deoxyribonucleic acid, is highlighted as the molecule encoding genetic information.
- RNA, specifically messenger RNA (mRNA), serves as an intermediary in conveying the genetic message from DNA to ribosomes for protein synthesis.
- The article emphasizes the complementary coding between DNA and RNA, where base pairs match up similar to the double helix structure of DNA.
Differences in Transcription:
- Notable distinctions in transcription processes between prokaryotes (bacteria) and eukaryotes are outlined.
- In prokaryotes, both transcription and translation occur in the cytoplasm, while in eukaryotes, transcription occurs in the nucleus, and mRNA is later translated in the cytoplasm.
- Accessibility of DNA to RNA polymerase differs between prokaryotes and eukaryotes due to structural variations such as histones and nucleosomes in eukaryotic DNA.
RNA Modification:
- The article mentions that mRNA produced in prokaryotic cells is not modified, while eukaryotic cells undergo modifications such as RNA splicing, 5' end capping, and the addition of a polyA tail.
Steps of Transcription:
- Transcription is broken down into five stages: pre-initiation, initiation, promoter clearance, elongation, and termination.
- The pre-initiation stage involves RNA polymerase and cofactors binding to DNA, creating an initiation bubble.
- Initiation in bacteria starts with RNA polymerase binding to the promoter, while in eukaryotes, transcription factors mediate this process.
- Promoter clearance, elongation, and termination are subsequent steps in which RNA polymerase synthesizes RNA, ensuring accuracy and completeness.
Termination of Transcription:
- Termination is highlighted as the final step, resulting in the release of the newly synthesized mRNA from the elongation complex.
- Eukaryotes undergo termination involving cleavage of the transcript and polyadenylation, where a poly(A) tail is added to the 3' end of the mRNA.

The article draws on reputable sources, including "Molecular Biology of the Gene" by Watson et al. and research articles such as those by Roeder and Yukihara, providing a solid foundation for the information presented. This comprehensive overview of transcription, coupled with the detailed breakdown of its steps, enhances our understanding of this fundamental biological process.