Concept explainers
Devoting a few sentences to each, describes the following structures or complexes and their effects on eukaryotic gene expression:
a. Promoter
b. Enhancer
c. Silencer
d. RISC
e. Dicer
To analyze:
The following structures and their effects on eukaryotic gene expression
Promoter
Enhancer
Silencer
RISC
Dicer
Introduction:
Gene regulation is an important feature of all living organisms. A regulatory sequence is a stretch of the DNA that can increase or decrease the expression of the genes. These genes can control the expression of one or more genes. Controlling genes can be negative or positive regulators. Negative regulators control gene regulation by inhibiting transcription or translation. These gene regulatory elements include insulators, enhancers, promoters, silencers.
Explanation of Solution
Promoter:
It is the regulatory part of the DNA that is responsible for the initiation of the gene. It can be
The eukaryotic promoter contains a TATA box that provides a binding site for TATA-binding protein. This protein helps in the formation of the RNA polymerase transcriptional complex.
Enhancer:
It is another regulatory sequence that can be bound by the activator proteins. It surges the transcription of the gene. It is the cis-acting gene. It can be existing upstream or downstream of the gene it regulates. It may be present near or very far from the genes they regulate.
Silencer:
It is a cis-acting sequence that binds to the regulatory sequence known as a repressor. By binding to the silencer, repressor prevents the binding of RNA polymerase and transcription of DNA sequence. Therefore, it does not allow the expression of the gene into proteins. Silencer sequence can be present upstream or downstream of the promoter sequence. In eukaryotes, silencer controls the gene regulation at the transcription level.
RISC:
It is also known as the RNA induced silencing complex. It is ribonucleoprotein that is involved in gene silencing. When a cell contains double-stranded RNA, the enzyme dicer cuts the double-stranded RNA into fragments. These fragments attach to the RISC which results in denaturation of double-stranded RNA into single-stranded RNA. One of the strands is a biologically active guide strand and second is the passenger strand. RISC binds to the guide strand that directs gene silencing.
Dicer:
It is an enzyme that converts double-stranded RNA to small interfering RNA. It consists of one double-stranded RNA binding site and two domains that have RNase activity. This RNase activity breaks the RNA. Dicer activates RISC that is crucial for RNA interference. Dicer also converts pre-miRNA to micro-RNA.
Transcriptional regulatory elements are nucleic acid sequences that are important in gene regulation.
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Chapter 15 Solutions
GENETIC ANALYSIS: AN INTEG. APP. W/MAS
- Identify the eukaryotic level of gene regulation. Choose the correct answer below. a. Pre- transcriptional control b. transcriptional control c. translational control d. post-translational control 1. in the fruit fly, genes from rRNA can be replicated more or less often compared to the rest of the chromatin depending on the needs of the cell. 2. in the human beta-globin, two introns are spliced out in order to produce the mature mRNA. 3. DNA methylation can change the degree of condensation of the chromatin. 4. The mouse REST gene is under the control of a promoter region that contains alternative promoters.arrow_forwardConsider a gene sequence whose promoter has acquired a mutation. Although this is a problem, this will not cause a missense mutation. Explain why the outcome in this scenario is NOT a missense mutation. Describe the purpose of a gene's promoter.arrow_forwardDefine the following terms: a. chemotaxis b. lac operon c. 80S ribosome d. mRNA secondary structure e. mRNA scanningarrow_forward
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- E. coli are grown on a medium containing lactose. Once glucose is added to the medium, the bacteria stop fermenting lactose. Which of the following BEST explains the observed effect? A. Cellular levels of cAMP are lowB.Glucose is bound to the promoter C. Repressor protein is bound to the operator D. Repressor protein is bound to the promoterarrow_forwardIn considering the 7 levels of gene regulation, which of the following mechanisms acts at first level? a. repressor binding to sequence blocking the promoter b. miRNA silencing c. differential processing of RNA d. protein modification e. answer may vary depending if this occurs in a prokaryote or a eukaryotearrow_forwardGive one example of a prokaryotic system of gene expression that is more complicated (duringtranscription at the promoter) than its corresponding eukaryotic system of gene expression.A. prokaryotes require general transcription factors to initiate transcriptionB. prokaryotes typically have activator and repressor DNA sequences thousands of nucleotides awayC. prokaryotes have three classes of RNA polymerasesD. prokaryotes always have their DNA tightly packed into higher-level structures than nucleosomesE. prokaryotes usually have polycistronic mRNAarrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning