Textbook Question
What are the sources of dsRNA? Diagram the mechanisms by which dsRNAs are produced and processed into small RNAs.
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13. Gene Regulation in Eukaryotes
Overview of Eukaryotic Gene Regulation
1:20 minutesProblem 18a
Textbook Question
The UG4 gene is expressed in stem tissue and leaf tissue of the plant Arabidopsis thaliana. To study mechanisms regulating UG4 expression, six small deletions of the DNA sequence upstream of the gene-coding sequence are made. The locations of deletions and their effect on UG4 expression are shown here. Explain the differential effects of deletions B and F on expression in the two tissues.
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Identify the role of the upstream DNA sequence in regulating gene expression. These sequences often contain regulatory elements such as promoters, enhancers, or silencers that control where and when a gene is expressed.
Examine the specific deletions (B and F) and their effects on UG4 expression in stem and leaf tissues. Deletion B may remove a regulatory element that is specific to one tissue, while deletion F may affect a different regulatory element.
Consider the possibility that deletion B removes an enhancer or promoter element required for UG4 expression in one tissue (e.g., stem tissue) but not the other (e.g., leaf tissue). This would explain why UG4 expression is reduced in one tissue but unaffected in the other.
Analyze deletion F and its potential to remove a regulatory element that is active in both tissues. If deletion F reduces UG4 expression in both stem and leaf tissues, it may have removed a shared enhancer or promoter element.
Conclude that the differential effects of deletions B and F on UG4 expression are likely due to the specific regulatory elements they disrupt. Deletion B may target a tissue-specific element, while deletion F may target a shared regulatory element.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Gene Expression Regulation
Gene expression regulation refers to the mechanisms that control the timing and amount of gene expression. This can involve various elements such as promoters, enhancers, and silencers, which interact with transcription factors to either promote or inhibit the transcription of a gene. Understanding these regulatory elements is crucial for analyzing how specific deletions can affect gene expression in different tissues.
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Tissue-Specific Expression
Tissue-specific expression is the phenomenon where certain genes are expressed in specific tissues or developmental stages. In the case of the UG4 gene in Arabidopsis thaliana, its expression in stem and leaf tissues may be influenced by unique regulatory sequences that respond differently to deletions. This concept is essential for understanding why deletions B and F might have varying effects on UG4 expression in these tissues.
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Deletion Mutations
Deletion mutations involve the removal of a segment of DNA, which can disrupt the normal function of genes and their regulatory elements. The impact of such deletions can vary based on their location relative to critical regulatory sequences. Analyzing how deletions B and F affect UG4 expression requires an understanding of how these mutations alter the gene's regulatory landscape in the context of the specific tissues involved.
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