Chapter 12

Chapter 12 - 1. It is a several methylguanisne cap. C. Euk....

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1. It is a several methylguanisne cap. C. Euk. RNA contains a poly-A tail 1. Adds a series of about 100 A nucleotides D. The eukaryotic RNA splicing reaction 1. removal of introns is catalyzed by RNA RNA acts as reaction catalyst one of the rare occasions 1. this process must occur with great fidelity 2. pre- mRNA contains a 5’ and 3’ splice site— these are conserved sequences found at the splice juctions of all eukaryotic pre-mRNAs. 1. In between the sequences there is a site called the branch site 2. Nucleophilic attack and release of exon 1 it forms a lop that is called the laret intermediate 3. Nucleophilic attack where exon 1 and exon 2 are spliced together 3. Spliceosome : complex of pre-mRNA, snRNA, and proteins. 4. Splicing is the result of two transesterification reactions (See Fig. 25-20) Chapter 12 Translation I. Introduction A. Translation is the process by which genetic information that has been passed to RNA from DNA is ultimately expressed as protein. Translation is the series of chemical events that catalyze the synthesis of polypeptides from a mRNA. B. Understanding translation requires an understanding the fundamental mechanisms that drive polypeptide synthesis from a mRNA. II. Understanding the genetic code how can a sequence of nucleotides composed of only 4 possible bases encode up to 20 different amino acids? A. Codon (triplet codon) = 3 base sequence that specify a single amino acid (i.e. each 3- base codon directs the incorporation of one specific amino acid into a polypeptide). 1. It doesn’t allow overlapping of codons
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2. The nature of the genetic code is also comma less IV> There are no nucleotides separating the codons it makes them pretty straight forward for ribosomes B. Each triplet code has 4 3 possible sequences = 64. Recall that proteins are composed of combinations of the 20 naturally occurring amino acids. C. The genetic code is 1. DEGENERATE 2. Nonoverlapping Example: THE BIG RED FOX ATE THE EGG THE IGR EDF OXA TET HEE GG The process of transcription and exon removal must be made with great fidelity III. Nature of the genetic code A. highly degenerate: 4 3 possible sequences = 64, only need 20. B.
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Chapter 12 - 1. It is a several methylguanisne cap. C. Euk....

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