Steps of Transcription - Online Tutor, Practice Problems & Exam Prep

Transcription involves three key steps: initiation, elongation, and termination. During initiation, RNA polymerase binds to the promoter region of DNA, with transcription factors aiding in eukaryotes. Elongation occurs as RNA polymerase synthesizes RNA by pairing free RNA nucleotides with the DNA template, moving in the 5' to 3' direction. Termination differs between prokaryotes and eukaryotes; eukaryotes produce a premature RNA that requires processing, while prokaryotes generate a ready-to-translate RNA. Understanding these processes is crucial for grasping gene expression and regulation.

Initiation of Transcription

In this video, we're going to begin our lesson on the steps of transcription. And so, the process of initiation of transcription. The second step is going to be elongation of transcription, and the third and final step is going to be the termination of transcription.

Moving forward, we're going to talk about each of these three steps of transcription in their own separate video starting with initiation. The initiation of transcription, initiation is referring to the beginning of transcription, and this involves the RNA polymerase binding to the promoter region on the DNA and separating the two strands of DNA. When those two strands of DNA are separated, that is going to allow the second step of transcription to begin. Now, it turns out that transcription in eukaryotes and prokaryotes is a little bit different. In prokaryotes, the RNA polymerase, which is the main enzyme involved in transcription, is going to bind to the promoter region on its own. However, in eukaryotes, transcription factor proteins are required for the RNA polymerase to bind to the promoter, and we'll be able to see that down below in our image. The unwinding of the DNA by the RNA polymerase is going to expose the DNA template strand, which the RNA polymerase can use as a guide to build the RNA.

If we take a look at our image, what you'll notice is on the left hand side, we're showing you initiation of transcription in prokaryotes, and on the right hand side, we're showing you initiation of transcription in eukaryotes. In the initiation, we know that the RNA polymerase is going to bind to the promoter and separate the two strands of DNA. Here in our image, the pink circle is representing the RNA polymerase, and the RNA polymerase is going to bind specifically to the promoter region on the DNA. You can also see downstream over here, you can see the terminator, which is going to be involved in the final process of transcription.

Over here on the right hand side, you'll see the same process, initiation of transcription in eukaryotes. The main difference that we're focusing on here is that in order for the RNA polymerase to bind to the promoter region in eukaryotes, these other proteins that we're representing as these yellow shapes here, are required, and those are the transcription factor proteins. In eukaryotes, RNA polymerase requires transcription factor proteins to bind to the promoter, and that will allow for the RNA polymerase to bind. In the eukaryotes here, and in the background, you can see that the transcription factors are bound, and that helps recruit the RNA polymerase so that the RNA polymerase can also bind to the promoter. Again, transcription initiation is going to allow for the second step of transcription to begin, which is elongation. We'll talk more about elongation, the second step of transcription, in our next video. So, I'll see you all there.

Elongation of Transcription

In this video, we're going to talk about the second step of transcription, which is the elongation of transcription. And so elongation is really just a word that means to elongate or make something longer, and the something that's being made longer is the RNA itself. Elongation is the process where the RNA polymerase enzyme is building, synthesizing, or elongating an RNA molecule. It does this by base pairing free RNA nucleotides that are floating around in the cell with the DNA template. By the end of the process, the RNA molecule that's being built is going to be carrying the message that's encoded by the DNA. Now the RNA polymerase enzyme, which is, again, the primary enzyme involved in transcription, is going to continue to move across the gene, unwinding the DNA as it moves and building the RNA as it moves in the 5'′ to 3'′ direction of the RNA. And so if we take a look at our image down below at the elongation of transcription, the DNA and RNA polymerase has unwound the DNA. So you can see that the DNA on the inside is unwound, and it's beginning to elongate or build that RNA molecule. By pairing free RNA nucleotides, these little guys here that are floating in the cell, each of these little squares represents free RNA nucleotides, and the RNA polymerase incorporates them into this growing RNA strand, by pairing these RNA nucleotides with the DNA template strand. And so this RNA polymerase is transcribing in this direction towards the right. So it will continue to transcribe the coding sequence, and so, this is representing the process of elongation. And, of course, during elongation, the mRNA molecule, is growing. It is elongating, and it's elongating from its 5'′ end to its 3'′ end. And the RNA polymerase will continue to elongate in this direction, continue to transcribe the gene until it reaches this terminator sequence that you see on the end here. And we'll talk more about this termination process in our next video. Now one thing that's important to note here is that in eukaryotic organisms, the RNA that is first transcribed is not the final RNA. Instead, it's a premature RNA or just a pre-mRNA. And so we'll get to talk more about the pre-mRNA later in our course. Now it's also interesting to note that a single gene can actually be transcribed simultaneously by several RNA polymerases to make more RNA if it's needed. And so while this mRNA here is being built by this RNA polymerase, it is possible for a second RNA polymerase to come and bind to the promoter and to transcribe this gene simultaneously where multiple RNA molecules are being built simultaneously from the same gene. And so that is just something to keep in mind. And so this here concludes our brief introduction to the elongation of transcription. And so in our next video, we'll get to talk about the third and final step of transcription, which is the termination of transcription. So I'll see you all there.

Elongation of Transcription

In this video, we're going to talk about the 3rd and final step of transcription, which is the termination of transcription. Termination refers to putting something to an end. So, the termination of transcription is the process that results in the end of transcription to produce an RNA molecule. It turns out that prokaryotes and eukaryotes actually differ in the way they terminate transcription. Specifically, in eukaryotes, eukaryotic termination forms a premature RNA molecule. This premature RNA molecule is not the final molecule in eukaryotic organisms and requires further modification through RNA processing, which we'll talk more about as we move forward in our course. However, in prokaryotes, the RNA molecule that's formed is not a premature RNA and does not require RNA processing. Premature RNA is only found in eukaryotic organisms.

If we take a look at our image below at the termination of transcription, you'll notice that the RNA polymerase is reaching this terminator sequence here, and the terminator sequence on the DNA initiates the process of termination. Ultimately, termination results in the RNA polymerase being released, and the RNA molecule being released. Again, in prokaryotic organisms, the RNA molecule is ready for translation immediately. However, in eukaryotic organisms, the RNA is a premature RNA, a pre-mRNA. This is not going to be the final version of the RNA in eukaryotic organisms. This RNA would have to undergo RNA processing before translation can take place. Again, this is applicable only for eukaryotes, not for prokaryotes.

This concludes our brief introduction to the termination of transcription, and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.

During which stage of transcription do the following processes take place?

1. RNA polymerase binds to the promoter.
2. The RNA transcript is released.
3. The RNA transcript extended.

• A. 1-termination; 2-initiation; 3-elongation.
• B. 1-initiation; 2-elongation; 3-termination.
• C. 1-elongation; 2-termination; 3- initiation.
• D. 1-initiation; 2-termination; 3-elongation.
• E. 1-termination; 2-elongation; 3-initiation.

Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?

• A. Anticodons.
• B. Ribosomes and tRNA.
• C. Transcription factors.
• D. Aminoacyl-tRNA synthetase.

Which of the following is the correct transcript of mRNA for the following DNA template?

DNA Template:3'-ATGAAGCCGAGTCAT-5'

• A. 3'-TACTTCGGCTCAGTA-5'
• B. 3'-AUGACUCGGCUUCAU-5'
• C. 3'-UACUUCGGCUCAGUA-5'
• D. 3'-ATGACTCGGCTTCAT-5'

During transcription of DNA to RNA:

• A. The RNA polymerase moves along the DNA in the 5' to the 3' direction.
• B. The 3' end of the RNA molecule is produced first.
• C. The RNA polymerase must first bind to a promoter sequence.
• D. Transcription is always initiated at a "start codon".

What happens during the initiation step of DNA transcription?

• A. The mRNA detaches from the RNA polymerase as the RNA polymerase leaves the DNA strand.
• B. RNA polymerase attaches to the DNA at the promoter sequence of the gene.
• C. A ribosome attaches to the initiation codon of a completed mRNA strand.
• D. RNA polymerase moves along the template strand of the DNA creating an mRNA strand.

Which of the following properties is NOT shared by RNA polymerase and DNA polymerase?

• A. Can initiate strand synthesis.
• B. Dependent on a DNA sequence template.
• C. Catalyzes phosphodiester bond formation.
• D. Cannot proofread using a 3'-to-5' exonuclease activity.
• E. Polymerizes nucleotides in a 5'-to-3' direction.

Here’s what students ask on this topic:

What are the three main steps of transcription?

The three main steps of transcription are initiation, elongation, and termination. During initiation, RNA polymerase binds to the promoter region of the DNA, with transcription factors aiding in eukaryotes. In elongation, RNA polymerase synthesizes RNA by pairing free RNA nucleotides with the DNA template, moving in the 5' to 3' direction. Termination occurs when RNA polymerase reaches a terminator sequence, resulting in the release of the newly synthesized RNA. In eukaryotes, this RNA is a premature RNA that requires further processing, while in prokaryotes, the RNA is ready for translation immediately.

How does the initiation of transcription differ between prokaryotes and eukaryotes?

In prokaryotes, RNA polymerase binds directly to the promoter region of the DNA to initiate transcription. In contrast, in eukaryotes, transcription factors are required to help RNA polymerase bind to the promoter. These transcription factors are proteins that assist in the recruitment of RNA polymerase to the promoter region, facilitating the initiation of transcription. This difference highlights the additional complexity in the regulation of gene expression in eukaryotic cells compared to prokaryotic cells.

What happens during the elongation step of transcription?

During elongation, RNA polymerase synthesizes the RNA molecule by adding RNA nucleotides that are complementary to the DNA template strand. The enzyme moves along the DNA, unwinding it as it goes, and elongates the RNA strand in the 5' to 3' direction. The RNA polymerase continues this process until it reaches a terminator sequence. In eukaryotes, the initial RNA produced is called pre-mRNA and requires further processing, while in prokaryotes, the RNA is ready for translation immediately.

What is the role of the terminator sequence in transcription?

The terminator sequence in transcription signals the end of the RNA synthesis process. When RNA polymerase reaches this sequence, it triggers the termination phase, causing the enzyme to release the newly synthesized RNA molecule and detach from the DNA template. In prokaryotes, the resulting RNA is ready for translation. In eukaryotes, the RNA produced is a premature RNA (pre-mRNA) that requires further processing, such as splicing, capping, and polyadenylation, before it can be translated into a protein.

Why is RNA processing necessary in eukaryotes but not in prokaryotes?

RNA processing is necessary in eukaryotes because the initial RNA transcript, known as pre-mRNA, contains non-coding regions (introns) that need to be removed. Additionally, eukaryotic pre-mRNA undergoes modifications such as the addition of a 5' cap and a poly-A tail to protect the RNA and facilitate its export from the nucleus. In contrast, prokaryotic RNA does not contain introns and is immediately ready for translation after transcription, eliminating the need for extensive processing.