ch.17 - Transcription & Genetic Code. Translation_need to print out.docx

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Biological Sciences
BIOSC 0150
Christine Dahlin- Universityof Pittsburgh Johnstown

1 General Biology 1 Chapter 17TranscriptionGenetic Code TranslationI TranscriptionCells have transcription and translation so that cells have the right proteins at the right times in the right places in order to do their jobs The central dogma by Francis Crick Transcription TranslationDNARNAprotein The building blocks of proteins are amino acids DNARNA and proteins written in 2 languages therefore multiple steps are needed In eukaryotes cellTranscriptionmake RNA mRNA using info in DNA st 1 step RNA madepremRNA or primary transcriptIn nucleusRNA complementary to DNAOut to cytoplasmnd 2 step RNA processed primary transcript now call messenger RNA mRNA rd 3 step RNA leaves nucleus translated into polypeptide w many amino acido Protein is made Bacteriahave no nucleus RNA made and processed immediately within the same place DO NOT go out to cytoplasmGenetic codeProblem there are 20 amino acid but only 4 nucleotide basesEach amino acid specified by 3 nucleotidesCodontriplet code 3 nucleotides1 amino acid o Codon set code for a specific amino acidThere are 64 combinations of nucleotides Only one DNA strand determined by gene used as template strand The codon table Each codon specifies an amino acidFigure 171The codon tableAlways written from 5 to 3There is a redundancythe first 2 letters of a codon are the same for throughout the entire row of mRNA base U C G ASpecial codonsstart codon AUG stop codons UAA UAG UGACodon code for the same amino acids in almost all organismsTranscriptionProcess of copying geneDNA serve as a templateRNA polymerase IIenzyme that made polymersdoes transcription RNA polymerase II opens DNA at a specific region on a gene o Polymerized ribonucleotides to make a complementary RNA strand
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