What are the 5 steps of RNA?

Q: Which is the 5 end of the RNA transcript?

5 End Capping At the end of transcription, the 5 end of the RNA transcript contains a free triphosphate group since it was the first incorporated nucleotide in the chain. The capping process replaces the triphosphate group with another structure called the cap. The cap is added by the enzyme guanyl transferase.

Q: Does RNA have a 5 end?

The 5′-end (pronounced five prime end) designates the end of the DNA or RNA strand that has the fifth carbon in the sugar-ring of the deoxyribose or ribose at its terminus.

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Learning Outcomes

Understand the basic steps in the transcription of DNA into RNA

Transcription takes place in the nucleus. It uses DNA as a template to make an RNA (mRNA) molecule. During transcription, a strand of mRNA is made that is complementary to a strand of DNA. Figure 1 shows how this occurs.

Figure 1. Overview of Transcription. Transcription uses the sequence of bases in a strand of DNA to make a complementary strand of mRNA. Triplets are groups of three successive nucleotide bases in DNA. Codons are complementary groups of bases in mRNA.

Transcription takes place in three steps: initiation, elongation, and termination. The steps are illustrated in Figure 2.

Figure 2. Transcription occurs in the three steps—initiation, elongation, and termination—all shown here.

Step 1: Initiation

Initiation is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter. This signals the DNA to unwind so the enzyme can ‘‘read’’ the bases in one of the DNA strands. The enzyme is now ready to make a strand of mRNA with a complementary sequence of bases.

Step 2: Elongation

Elongation is the addition of nucleotides to the mRNA strand. RNA polymerase reads the unwound DNA strand and builds the mRNA molecule, using complementary base pairs. There is a brief time during this process when the newly formed RNA is bound to the unwound DNA. During this process, an adenine (A) in the DNA binds to an uracil (U) in the RNA.

Step 3: Termination

Termination is the ending of transcription, and occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA.

This video provides a review of these steps. You can stop watching the video at 5:35. (After this point, it discusses translation, which we’ll discuss in the next outcome.)

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Transcription is the chemical synthesis of RNA from a DNA template

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Updated on March 01, 2021

DNA or deoxyribonucleic acid is the molecule that codes genetic information. However, DNA can't directly order a cell to make proteins. It has to be transcribed into RNA or ribonucleic acid. RNA, in turn, is translated by cellular machinery to make amino acids, which it joins together to form polypeptides and proteins

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:

Pre-Initiation

Atomic Imagery / Getty Images

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.

Initiation

Forluvoft / Wikimedia Commons / Public Domain

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.

Promoter Clearance

Ben Mills / Wikimedia Commons / Public Domain

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.

Elongation

Forluvoft / Wikimedia Commons / Public Domain

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.

Termination

Forluvoft / Wikipedia Commons / Public Domain

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.

Watch Now: Scientists Want To Store All Information on DNA

What are the steps of RNA?

RNA then undergoes translation to make proteins. The major steps of transcription are initiation, promoter clearance, elongation, and termination.

Which is the 5 end of the RNA transcript?

5' End Capping At the end of transcription, the 5' end of the RNA transcript contains a free triphosphate group since it was the first incorporated nucleotide in the chain. The capping process replaces the triphosphate group with another structure called the "cap". The cap is added by the enzyme guanyl transferase.

Does RNA have a 5 end?

The 5′-end (pronounced "five prime end") designates the end of the DNA or RNA strand that has the fifth carbon in the sugar-ring of the deoxyribose or ribose at its terminus.

What is the process of RNA transcription?

Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins). RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule. Transcription ends in a process called termination.