11-2-06 BIMM100 Assign5

11-2-06 BIMM100 Assign5 - BIMM 100 FALL 2006 Assignment 5...

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BIMM 100 FALL 2006 Assignment 5 1. Name the three different types of RNA that are required for the process of translation and describe their functions. Name the RNA polymerase responsible for synthesizing each type of RNA. mRNA: encodes the genetic information from transcribed DNA and serves as the template for polypeptide synthesis. mRNA is synthesized by RNA Pol II. tRNA: deciphers the codons in mRNA. It can do this because each tRNA has an anticodon nucleotide sequence that base-pairs to the complementary mRNA codon. The amino acid carried by that specific tRNA can then be added to the growing peptide chain. RNA Pol III is in charge of the synthesis of tRNA. rRNA: associates with proteins to form ribosomes, which physically move along the mRNA molecule to catalyze the assembly of the a.a. into peptide chains. Pre-rRNA is synthesized by RNA Pol I, but 5s rRNA is synthesized by RNA PolIII. 2. Consider the modifications that occur during mRNA maturation: (a) What is the function of the 5’ cap and 3’ polyA tail structures present on mature Eukaryotic mRNAs? 5’ capping and 3’ polyadenylation are essential processes for the maturation of mRNA; both of the structures produced by these processes can protect mRNA from degradation by RNases and also help to target the mature mRNA for export to the cytoplasm for translation. In addition, they promote the recruitment and recycling of ribosomes to perform translation and also increase the efficiency of translation. (b) For 5’ capping, which base is added to the 5’ end of the pre-mRNA? 7-Methylguanylate is added to the 5’ end of the pre-mRNA and there is a 5’-5’ linkage of the cap to the mRNA strand. (c) Describe the basic steps of 3' polyadenylation and name the enzyme responsible for adding the A's. The 3' splice signals (AAUAAA and the downstream G/U rich region) are recognized by the machinery, there is cleavage between the 2 signals and Poly(A) polymerase (PAP) adds A’s to create a poly(A) tail of 200~250 A’s. PAP is an RNA polymerase and doesn’t use a template. (d) What are the general modifications required for tRNA maturation?
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11-2-06 BIMM100 Assign5 - BIMM 100 FALL 2006 Assignment 5...

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