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U-M BIOLOGY 172 - Lecture 7

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Lecture 7I. The Central Dogma A. DNA1. Copy Functioni. faithfully copied during cell division2. Expression Function i. encondes cellular products that determine phenotypeB. Translation1. mRNAi. specific the sequence of amino acids in a protein2. Aminoacly tRNA suntheasesi. binds free amino acids with uncharged tRNAii binds each amino acid to their specific tRNA3. tRNAi. links nucleic acid information to amino acids: pusicallt brings amino acids to the ribosomesii. Short RNAs with intramolecular base pairing( H bonds)iii. One part anticodon base paird with codon of mRNAiv. one end is attached to a specific amino acid4. Ribosomesi. responsible for translation and synthesizing proteinsii. Has t2 subunits, the small subunit(under mRNA) and the Large subunit(above mRNA)a. the large subunit indculde three binding sites1) Exit site2) Peptidyl site3) Aminoacly site5. Inisitaion Factors6. Elongation factors7. Release Factors8. rRNAi. component of ribosomes9. Basic featuresi. synthesis of a polypeptide using information in RNAsii. carried out by a ribosmeiii. occurs in the cytosol of the RNAiv. polypetides are synthesized from ther amino (N) terminus to their carboxyl (C) terminusv. a single mRNA can be translate many time by biosomes and multipleribosomes can simultanesouly translate the same mRNAvi. The polypeptide produced from translation often must be modified before it is a functional protein =10. Initiationi. small subunit of ribsome attaches 5’ end of mRNA(riobomse bindingsite) in prokaryotes..attached to 5’ cap in eukaryotesii. intiator aminoacly tRNA bind to start codoniii. large subunit of ribosme binds and the initator tRNA occupies the Psite11. Elongation i. incoming aminocly tRNA to the A site of the large ribsome subunitii. Peptide bond formation between the amino acids of the tRNA that will form the new protein iii. Translocationa. ribosome moves along mRNA and the aminolcy tRNA moves to the next site in the large subunit in the ribosome12. Termination- protein synthesis ends when the ribosme encounters a stopcodon in A site and cleave polypeptide from tRNAi. relase factor protein binds to the stop codon in A site and cleaves ii. polypeptide is relasesediii. ribosomal subunits and other components dissociate*In eukaryotes, translation is initiated only at the 5’cap. …..In prokaryotes, initiation takes place at any Shine-Dalgarno Sequence (ribosome binding site); this mechanism allows a single mRNA to include coding sequences for multiple polypeptides. This is called polycistrony.*Monocistronic mRNA*Polycistronic mRNAIII. Genetic Codes- the relationship between nucleotide sequence and amino acid sequenceA. is a triplet codeB. Has no ambiguityC. Has some redundancyD. the triplet code is non overlapping and continuous….3 nucleotides in mRNA= 1codonE. has a specific start codon(AUG-Metionine)F. Includes three stop codonsG. is nearly


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