Introduction to Regulation of Gene Expression - Online Tutor, Practice Problems & Exam Prep

Gene expression regulation occurs in both prokaryotic and eukaryotic cells, involving a two-step process: transcription (DNA to RNA) and translation (RNA to protein). Regulation can happen at five stages: chromatin rearrangements, transcriptional control, post-transcriptional control, translational control, and post-translational control. Positive gene regulation stimulates gene expression, while negative regulation prevents it, akin to a light switch. Understanding these mechanisms is crucial for grasping how cells control protein production and respond to environmental changes.

Introduction to Regulation of Gene Expression

In this video, we're going to begin our introduction to regulation of gene expression. It's important to know that both prokaryotic and eukaryotic cells have the ability to regulate or control their gene expression. Recall from our previous lesson videos that gene expression is just referring to the ability to express a gene, or to create the final product that's associated with a gene. In many cases, the final product of a gene is going to be a protein.

If we take a quick look at our image below, notice we're showing you an image that's showing gene expression, because gene expression typically requires a 2-step process. The first step is transcription which converts, or which uses DNA to build RNA. The second step of gene expression is translation, which uses the RNA to build a protein. Gene expression, basically using the DNA to build proteins, has many different stages of regulation. Gene expression can be controlled or regulated at any of 5 stages. Notice that we have these 5 stages of regulation or control numbered below. These numbers correspond with the numbers that you see in our image.

The very first stage of gene expression is going to be chromatin rearrangements. Chromatin rearrangements are just referring to the regulation of chromatin conformations and, basically, controlling DNA's accessibility for transcription. We'll get to talk more about chromatin rearrangements later in our course. The second stage of regulation of gene expression is transcriptional control. This will be controlling or regulating transcription, regulating RNA polymerase's binding to the promoter, and the initiation of transcription. Most prokaryotic gene regulation actually occurs at this transcriptional control level or stage. We'll be able to talk more about transcriptional control as we move forward in our course.

The third stage of gene expression regulation is post-transcriptional control, where "post" is a root that means "after". So post-transcriptional control is going to be the regulation of modifications to the RNA after transcription has already occurred. The fourth stage of regulation that we have is translational control. Of course, translational control is going to be regulating the initiation and elongation steps of translation. The fifth and final stage of gene expression regulation is post-translational control. "Post" again means "after", so post-translational control is going to come after translation. It regulates modifications to proteins after translation has occurred.

We'll get to talk more about each of these stages of gene expression regulation as we move forward in our course. But if we take a look at our image below, you can see we're showing you an image of the 5 stages of gene expression and regulation of gene expression. Prokaryotes like bacteria and archaea tend to use transcriptional control as their primary way of regulating their gene expression, as highlighted above. However, in eukaryotes, gene regulation can actually occur at any of these 5 stages. Moving forward in our course, we're going to talk more about gene regulation and we will start by talking about transcriptional control at the prokaryotic level. Later in our course, we'll double back and talk more about each of these other stages of regulation. But for now, this here concludes our discussion on gene expression as we move forward. So, I'll see you all in our next video.

Positive vs Negative Gene Regulation

In this video, we're going to talk about positive versus negative gene regulation. Cells can regulate their gene expression in one of two different ways. The first way is via positive gene regulation and the second way is via negative gene regulation. Positive gene regulation is going to stimulate gene expression by turning on the gene so that the gene's final product is actually being made at a higher rate. Negative gene regulation, on the other hand, prevents gene expression; it turns out that positive and negative gene regulation can actually resemble a light switch in a way. Just like light switches can be turned on to turn on the light and can be turned off to turn off the light, genes can also be turned on and turned off via positive and negative regulation.

Over here on the left-hand side of our image, notice that we're showing you a light switch being turned on into the on position. This is going to resemble positive gene regulation, the stimulation of gene expression by turning the gene on. Notice over here on the right-hand side of our image, we're showing you the light switch being turned into the off position. This is going to resemble negative gene regulation since with negative gene regulation, this prevents gene expression by turning off the gene.

As we move forward in our course, we're going to see more specific examples of both positive regulation and negative regulation as well. But for now, this here concludes our brief introduction to positive and negative gene regulation, and we'll be able to get some practice applying the concepts that we've learned as we move forward in our course. So I'll see you all in our next video.

Post-translational control refers to:

• A. Regulation of gene expression after transcription.
• B. Regulation of gene expression after translation.
• C. Control of epigenetic activation.
• D. Period between transcription and translation.

Which of the following is an example of positive regulation of gene expression?

• A. Transcription is halted on a specific gene to limit the amount of protein being created by the gene's expression.
• B. The protein that is translated is immediately degraded by the cell before it can serve its function.
• C. Elongation of translation comes to a stop and the ribosome dissociates when a regulatory protein binds.
• D. A protein binds to DNA and then stimulates the initiation of transcription of a specific gene.

In prokaryotes, control of gene expression usually occurs at the

• A. Splicing of pre-mRNA into mature mRNA.
• B. Post-translational control level.
• C. Transcriptional control level.
• D. All of the above.

Here’s what students ask on this topic:

What are the stages of gene expression regulation in eukaryotic cells?

Gene expression regulation in eukaryotic cells occurs at five stages: chromatin rearrangements, transcriptional control, post-transcriptional control, translational control, and post-translational control. Chromatin rearrangements involve modifying the DNA's structure to control its accessibility for transcription. Transcriptional control regulates the binding of RNA polymerase to the promoter and the initiation of transcription. Post-transcriptional control involves modifications to RNA after transcription, such as splicing and editing. Translational control regulates the initiation and elongation steps of translation, determining how efficiently proteins are synthesized. Finally, post-translational control involves modifications to proteins after translation, such as phosphorylation or glycosylation, affecting their function and stability.

How does positive gene regulation differ from negative gene regulation?

Positive gene regulation stimulates gene expression by turning on the gene, leading to an increased production of the gene's final product. It is akin to turning on a light switch. In contrast, negative gene regulation prevents gene expression by turning off the gene, similar to turning off a light switch. Positive regulation enhances the rate of transcription and translation, while negative regulation inhibits these processes. Both mechanisms are crucial for cells to adapt to environmental changes and maintain homeostasis.

Why is transcriptional control the primary method of gene regulation in prokaryotes?

Transcriptional control is the primary method of gene regulation in prokaryotes because it is the most efficient way to regulate gene expression in these organisms. Prokaryotes, such as bacteria, have simpler cellular structures and fewer regulatory mechanisms compared to eukaryotes. By controlling the initiation of transcription, prokaryotes can quickly respond to environmental changes and conserve energy by only producing proteins when needed. This level of control is crucial for their survival and adaptability.

What is the role of chromatin rearrangements in gene expression regulation?

Chromatin rearrangements play a crucial role in gene expression regulation by altering the structure of chromatin, which affects the accessibility of DNA for transcription. Chromatin can exist in a condensed (heterochromatin) or relaxed (euchromatin) state. When chromatin is relaxed, transcription factors and RNA polymerase can access the DNA more easily, promoting gene expression. Conversely, when chromatin is condensed, the DNA is less accessible, and gene expression is repressed. These rearrangements are essential for regulating which genes are expressed at specific times and in response to various signals.

What are the differences between post-transcriptional and post-translational control?

Post-transcriptional control involves modifications to RNA after transcription has occurred. These modifications can include splicing, editing, and the addition of a 5' cap and poly-A tail, which affect RNA stability, localization, and translation efficiency. Post-translational control, on the other hand, involves modifications to proteins after translation. These modifications can include phosphorylation, glycosylation, ubiquitination, and cleavage, which affect the protein's function, stability, localization, and interactions with other molecules. Both types of control are essential for fine-tuning gene expression and ensuring proper cellular function.