Protein Synthesis I Transcription Crick s Central Dogma DNA makes RNA makes Protein Evidence for a role for RNA in protein synthesis RNA is similar to DNA RNA is found in cytoplasm not nucleus protein is made in cytoplasm cytosol ribosomes are partially made from RNA DNA vs RNA deoxy vs oxy Deoxyribonucleic acid vs Ribonucleic DNA is double stranded RNA is single stranded DNA has thymine RNA has uracil Three types of RNA mRNA messenger RNA carries code from DNA in nucleus to ribosome in cytoplasm cytosol tRNA transfer RNA transfers amino acids from cytosol to growing protein on ribosome rRNA ribosomal RNA is a structural molecule that partially makes up the ribosome Two parts to protein synthesis transcription information from DNA is copied onto mRNA in nucleus occurs in nucleus translation manufacture of a protein occurs in the ribosome from instructions carried on mRNA occurs in cytoplasm Summary of process DNA stays in nucleus un winds information i e the order of bases is copied onto mRNA mRNA exits nucleus and goes to ribosome information is read and amino acids come together to make protein Transcription DNA unravels RNA bases are strung together onto template strand of DNA process is mediated by an enzyme called RNA polymerase strand of mRNA is manufactured released Difference between protein synthesis and DNA replication Stiches back up after the bubble forms and mRNA does its job amplified to the point that thousands of mRNA copies from the DNA Only 3 5 of the human genome codes for protein ALL is transcribed onto mRNA even the non coding DNA Exon A series of nucleotides within a gene sequence that does code for a protein Intron a series of nucleotides within a gene sequence that does not code for a protein introns are spliced out to form an edited mRNA transcript Alternate splicing you can assemble all these in a series of ways Why they can code for so many different protein Summary of protein synthesis again information i e the order of bases on DNA is copied onto mRNA mRNA exits nucleus and goes to ribosome where information is read and amino acids come together to make protein Translation Protein Synthesis II Translation 1 mRNA arrives to ribosome 2 Amino acids are brought to ribosome and are strung together into proteins Ribosome constructed of RNA ribosomal RNA and protein has two parts small subunit and large subunit Codon a sequence of three bases in an mRNA molecule that codes for a single amino acid The genetic code sequences of RNA bases codons that specify amino acids notice the start and stop codons Universal for all living organisms Translation third type of RNA transfer RNA one end of tRNA binds with a specific amino acid the other end of tRNA the anti codon base pairs with the codon of mRNA SO tRNA and amino acids float freely in the cytosol mRNA arrives to the ribosome a succession of amino acids are brought to the ribosome by tRNA and linked together to form a protein Detail I Initiation mRNA arrives to small subunit tRNA with anti codon UAC arrives and binds to the AUG codon II Elongation large sub unit arrives with A and P sites a second tRNA binds to the mRNA codon in the A site a peptide bond forms this breaks the bond between the original tRNA and mRNA the ribosome cinches its way down the mRNA moving 3 bases along a new mRNA codon is moved into the A site III Termination Elongation continues until the stop codon is reached no new tRNA binds the P site tRNA molecule releases the protein chain the ribosomal complex comes apart and the released protein folds up Watch Protein Synthesis on YouTube the first 3 or 4 minutes of the video is classroom lesson but if you can get beyond that the rest is performance art circa 1971 Not to be missed http www youtube com watch v u9dhO0iCLww Point mutations single base mutation insertion deletion mis sense changes codon for ONE amino acid substitution frame shift scrambles all subsequent amino acids insertion or deletion of three bases restores frame but results in mis sense One side of the tRNA attaches to the codon what on the other side Amino Acid
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