Essential Elements of Biochemistry BCHM 3050 Dr Srikripa Chandrasekaran Lecture 3 9 15 Notes The Genetic Code Protein Synthesis I II Introduction to Translation A HIV is a virus that has genetic material it has RNA at first and once it gets into a host it makes the RNA into DNA and it integrates this DNA into the genome of the host Cracking of the Genetic Code A Several scientists came to this same conclusion but Nirenberg and Matthaei won the race B Everything needed for translation in is the bacterial extract except mRNA which has to be made new every time C The key difference between DNA polymerase and RNA polymerase is that RNA polymerase does not need a primer DNA polymerase requires a primer in order to start extending a DNA chain D 1st observation there is a code the nitrogenous bases code for specific amino acids E Then when they put 2 different alternating bases in a sequence they got 2 different amino acids and 2 different amino acid sequence combinations 1 2 different base sequences UCU CUC UCU CUC CUC UCU CUC UCU F They determined that there is probably more than one combination that codes for a specific amino acid G Then they put 3 nucleotides together and they were able to figure out that 3 bases 1 amino acid III The Complete mRNA Genetic Code A Some amino acids are coded for by more than 1 triplet B Leucine is the most abundant amino acid in the body so it has the most amount of different triplet codes C Methionine AUG is the start codon and must be present in order for amino acids to be coded in the body start translating where there is an AUG and ignore everything that comes before this start codon D The stop codons end translation E The start and stop codons are where translation starts and where translation stops and stop transcription F Promoter and terminator are present for transcription and they start G Each amino acid has about 4 codons that code for it the third position of the codons varies while the first and second positions are the same between the 4 different codons the 3rd nitrogenous base is called a degenerative base 1 H There is only 1 codon that codes for tryptophan so it is likely the least abundant amino acid I All of the codons are read 5 3 J The more codons that code for a specific amino acid the more abundant that amino acid is IV Codons vs Anticodons A Make sure you read the tRNAs 5 3 when trying to code for an amino acid 5 CAU3 anti codon 3 GUA5 mRNA codon So the amino acid you code for is methionine AUG B 64 total codons and 20 total amino acids C In order to find the total number of possible base combinations of an organism you must take the total number of bases and raise it to the power of the number of bases that have to be combined to make an amino acid so if you have 4 nucleotide bases and 3 together make a codon than 43 64 which gives you the total number of possible base combinations or codons D There are 20 special enzymes that are specialized for the 20 amino acids V VI Requirements for Protein Synthesis A Ribosomes come in a small and large subunit B Need energy both ATP and GTP C GTP serves are the primary energy source rather than ATP Ribosome Structure A A site also called acceptor site B There are 3 main spots in the ribosome C Which codon is sitting in which spot tells you how translation will D 2 tRNAs take up A and P sites and the two tRNAs transfer amino acids E The acceptor site accepts new tRNA all of the time F The 1st codon amino acid sits at the P Site G The 2nd and 3rd codons amino acids sit at the A Site the A Site has 2 proceed to form a peptide amino acids 2
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