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Chapter 15: Problem 19

What are the subcategories within eukaryotic promoters? How do enhancers and silencers differ from promoters?

Short Answer

Expert verified
Answer: The main difference between eukaryotic promoters, enhancers, and silencers is their function in gene expression regulation. Promoters initiate gene transcription by providing a binding site for the RNA polymerase II and other general transcription factors, while enhancers and silencers are regulatory elements that influence the rate of transcription by binding to activators or repressors, respectively. Enhancers and silencers can be located far away from the genes they regulate and can function in both orientations, regardless of their distance from the transcription start site.

Step by step solution

01

Define eukaryotic promoters

Eukaryotic promoters are DNA sequences that are located upstream of the transcription start site (TSS) and responsible for the initiation of gene expression. RNA polymerase II and other general transcription factors bind to these promoters to form the pre-initiation complex (PIC), which is essential for the transcription process.
02

Identify the subcategories within eukaryotic promoters

There are two main subcategories of eukaryotic promoters: 1. TATA-box containing promoters (TATA promoters): These promoters contain a conserved "TATA" sequence (TATAAA) about 25-30 bp upstream of the transcription start site. This TATA sequence serves as a binding site for the TATA-binding protein (TBP), which is a component of the transcription factor IID (TFIID). 2. TATA-less promoters: These promoters do not have a TATA-box sequence but contain other regulatory elements, such as initiator elements (INR) and downstream core promoter elements (DPE). These promoters depend on other specific transcription factors for initiation of transcription.
03

Define enhancers and silencers

Enhancers and silencers are both cis-regulatory elements that play a role in the regulation of gene expression. - Enhancers: These are DNA sequences that can enhance the transcription of a target gene when bound by specific transcription factors called activators. They can function even when they are located far away from the promoter, and they can function distance and orientation-independent in both directions. - Silencers: These are DNA sequences that can repress the transcription of a target gene when bound by specific transcription factors called repressors. Just like enhancers, they can function at a distance from the promoter and have orientation-independent activity.
04

Differentiate between promoters, enhancers, and silencers

- Promoters are DNA sequences that initiate gene transcription by providing a binding site for the RNA polymerase II and other general transcription factors. They are typically located near the transcription start site of a gene. - Enhancers and silencers are both regulatory elements that influence the rate of transcription by binding to activators or repressors, respectively. Unlike promoters, they can be located far away from the genes they regulate and can function in both orientations, regardless of their distance from the transcription start site.

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Most popular questions from this chapter

Both attenuation and riboswitches rely on changes in the secondary structure of the leader regions of mRNA to regulate gene expression. Compare and contrast the specific mechanisms in these two types of regulation.

Compare the control of gene regulation in eukaryotes and prokaryotes at the level of initiation of transcription. How do the regulatory mechanisms work? What are the similarities and dif- ferences in these two types of organisms in terms of the specific components of the regulatory mechanisms? Address how the differences or similarities relate to the biological context of the control of gene expression.

What are transcription factors? What cis-acting elements do they bind?

Many eukaryotic promoter regions contain CAAT boxes with consensus sequences CAAT or CCAAT approximately 70 to 80 bases upstream from the transcription start site. How might one determine the influence of CAAT boxes on the transcription rate of a given gene?

The locations of numerous \(\operatorname{lac} I^{-}\) and \(\operatorname{lac} I^{S}\) mutations have been determined within the DNA sequence of the lacI gene. Among these, \(l a c I^{-}\) mutations were found to occur in the \(5^{\prime}\) -upstream region of the gene, while \(l a c I^{S}\) mutations were found to occur farther downstream in the gene. Are the locations of the two types of mutations within the gene consistent with what is known about the function of the repressor that is the product of the lacI gene?
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