RNAi in Eukaryotic Cells: Examples and Applications in AP Biology

📚 RNAi in Eukaryotic Cells: Quick Study Guide

• 🧬 RNA Interference (RNAi): A biological process where RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules.
• 🎯 Mechanism: RNAi involves small interfering RNAs (siRNAs) and microRNAs (miRNAs).
• ✂️ siRNAs: Typically originate from long double-stranded RNA molecules that are cleaved by the enzyme Dicer into shorter fragments (approximately 21-23 nucleotides).
• 🌱 miRNAs: Endogenous non-coding RNAs that regulate gene expression. They are transcribed from DNA but are not translated into protein.
• ⚙️ RISC (RNA-induced silencing complex): A multiprotein complex that incorporates one strand of the siRNA or miRNA duplex. The RISC uses the bound siRNA or miRNA as a template for recognizing mRNA that is complementary to the siRNA or miRNA.
• 🚫 Gene Silencing: Binding of the siRNA/miRNA-RISC complex to the mRNA can lead to mRNA degradation or translational repression, effectively silencing the gene.
• 🧪 Applications: RNAi is used in research to study gene function and has potential therapeutic applications for treating diseases.

🧪 Practice Quiz

1. What is the primary function of RNA interference (RNAi) in eukaryotic cells?

   1. A. To enhance protein synthesis
   2. B. To inhibit gene expression
   3. C. To repair damaged DNA
   4. D. To regulate cell division

2. Which enzyme is responsible for cleaving long double-stranded RNA molecules into shorter fragments during RNAi?

   1. A. Polymerase
   2. B. Ligase
   3. C. Dicer
   4. D. Helicase

3. What does RISC stand for in the context of RNAi?

   1. A. RNA-induced silencing complex
   2. B. Ribonucleic stabilizing compound
   3. C. RNA inhibiting structural component
   4. D. Replication initiation site complex

4. What is the typical size of siRNA fragments generated during RNAi?

   1. A. 5-10 nucleotides
   2. B. 10-15 nucleotides
   3. C. 21-23 nucleotides
   4. D. 30-35 nucleotides

5. Which of the following is a potential outcome of the binding of an siRNA/miRNA-RISC complex to mRNA?

   1. A. Increased mRNA transcription
   2. B. mRNA degradation
   3. C. Enhanced protein folding
   4. D. DNA replication

6. What is the origin of miRNAs in RNAi?

   1. A. Synthesized in the ribosome
   2. B. Transcribed from DNA
   3. C. Imported from the cytoplasm
   4. D. Created by Dicer from mRNA

7. Which of the following is a common application of RNAi technology?

   1. A. Enhancing photosynthesis
   2. B. Studying gene function
   3. C. Increasing mutation rates
   4. D. Producing biofuels