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Protein Synthesis Transcription and Translation:the Central Dogma DNA Transcription RNA Translation Protein RNA RNA: ribonucleic acid Carries out protein synthesis Differences from DNA: different sugar (ribose) single strand different base no thymine URACIL instead 3 Types of RNA: • Messenger RNA: (mRNA) carries nucleotide sequence from nucleus to ribosome • Transfer RNA: (tRNA) picks up amino acid in cytoplasm and carries them to ribosome • Ribosomal RNA: (rRNA)found in ribosome, joins mRNA and tRNA; forms protein Process of Transcription • Transcription- process that makes mRNA from DNA 1. DNA unzips into 2 separate strands A. DNA Helicase is the enzyme that breaks Hbond 2. Free floating RNA NITROGEN BASES in the nucleus pair up w/unzipped DNA: A. Cytosine(C) pairs with Guanine(G) * (G) - (C) B. Adenine (A) pairs with Uracil (U) * (A) - (U) C. Thymine (T) pairs with Adenine (A) ***remember (T) is only with DNA Transcription RNA Polymerase is the enzyme that strings together the complimentary strand of RNA nucleotides . 7 Transcription DNA ATCGTTACATGC RNA UAGCAAUGUACG A-U T-A G-C C-G 3. After all the pairing is done: • a single strand of RNA has been produced. Transcription - Genetic code from DNA is transferred to mRNA -The code obtained from DNA lets the mRNA know which amino acids to pick up. Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase RNA DNA Transcription Similar to DNA Replication: - Occur within the nucleus of eukaryotic cells. - Both catalyzed by large, complex enzymes - Both involve unwinding DNA - Both involve specific base-pairing Transcription Different to DNA Replication: - Cell may need hundreds or thousands of copies of certain proteins. - Makes a single stranded compliment of only a segment of DNA and only when it is needed. - Process can occur over and over again. Translation Converts the mRNA message into a polypeptide. One or more polypeptides make up a protein Translation Nucleus Lysine Phenylalanine Methionine tRNA Ribosome mRNA Start codon mRNA Translation 20 Amino acids are used as the “language” of proteins. Bases : Nucleic Acids Amino Acids : Proteins Translation Codon: 3-nucleotide sequence that codes for an amino acid * Many amino acids are coded for by more than one codon Ex: Leu * The first two nucleotides- generally most important in coding 17 Translation START CODON (AUG) : Methionine (MET) STOP CODONS: UAA , UAG, UGA 18 Translation Codons must be read in the right order - reading frame Change in the reading frame- change in the protein 19 Translation GENETIC CODE: - Shared by almost all organisms- even viruses - “Universal” code - Common nature of the genetic code suggests that almost all organisms arose from a common ancestor. - Scientists can insert a gene from one organism into another to make proteins 20 Translation DNA TRY IT OUT! TACCCGTTACGAATT mRNA Amino Acid 21 Translation DNA TRY IT OUT! TAC/CCG/TTA/CGA/ATT mRNA AUG/GGC/AAU/GCU/UAA Amino Acid Met-Gly-Asn-Ala-STOP 22 Translation MAKE A PROTEIN: Write out a 30 base DNA sequence ( pink paper) ( Blue paper) Show DNA —> RNA —> Amino Acid sequence Exchange pink sheet with a partner! 23 Translation Ribosomes- site where proteins are made Small subunit: holds the mRNA strand Large subunit: holds on to the growing protein Translation tRNA : Carries amino acids from the cytoplasm —> ribosome One end is attached to a certain amino acid Other end—> Anti-codon : recognizes a certain codon 25 26 Translation (continued) Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA mRNA Ribosome Translation direction