Study+questions+Lecture+18+Regulatory+RNA++KEY - Study...

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Study questions Lecture 18 KEY – Regulatory RNA Question 1. You have developed a computer algorithm to identify RNA secondary structure within intron sequences in mammalian cells. You find a sequence you predict would fold into a miRNA precursor in a gene called IPASSED . There is a gene in the genome called MISERY that contains complementary sequences in the 3‟ untranslated region, but they would not form a perfectly paired hybrid. (a) This miRNA precursor would likely be processed to miRNA by which enzymes? (circle all that apply). Next to the enzyme(s) that you select, indicate whether this processing step would occur in the nucleus or the cytoplasm ? 1. Dicer Cytoplasm 2. Drosha Nucleus 3. Argonaute 4. Histone methyl transferase 5. RITS 6. RNAse III (b) Would you expect the miRNA found in IPASSED to activate or repress MISERY expression? (circle one) (c) What is the likely fate of MISERY in a cell where IPASSED is expressed? (circle one) i. Chromatin surrounding the MISERY gene will be highly methylated. ii. The MISERY transcript will be subject to cleavage by Argonaute. iii. Translation will be blocked and the message will eventually degrade. iv. The MISERY protein can now bind to a histone deacetylase. Question 2 . You have purified large quantities of Dicer and you want to assay its activity. What kind of substrate would you use for your assay? Consider the product of the assay and how you will detect it. Draw a gel that represents the mobility of your substrate in the absence and presence of Dicer. You will need a double-stranded RNA substrate that is labeled throughout with 32P isotope. (If it is end-labeled then only the very last part will be detected on the gel after cleavage with Dicer). In the presence of Dicer, the substrate will be cleaved into 21 bp siRNA fragments that will run with faster mobility during gel electrophoresis than the substrate. Without Dicer you will see the slow migrating substrate.
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Question 3 . Which of the following is TRUE of pre-miRNAs: (mark all that are correct) __X__ are processed by Dicer to generate mature miRNAs. ____ can silence genes via the sequence-specific degradation of complementary DNA sequences. ____ are processed by the „Slicer‟ activity of Argonaut to generate mature miRNAs.
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This note was uploaded on 02/26/2012 for the course MCB 121 taught by Professor Gasser during the Winter '09 term at UC Davis.

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Study+questions+Lecture+18+Regulatory+RNA++KEY - Study...

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