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Chapter 12: Protein Synthesis What is DNA?

Chapter 12: Protein Synthesis What is DNA?. Chapter 13 Protein Synthesis - Overview. The DNA of the gene is transcribed into RNA Which is translated into protein The flow of genetic information from DNA to RNA to Protein is called the CENTRAL DOGMA. DNA. Transcription. RNA.

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Chapter 12: Protein Synthesis What is DNA?

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  1. Chapter 12: Protein SynthesisWhat is DNA?

  2. Chapter 13 Protein Synthesis - Overview The DNA of the gene is transcribed into RNA Which is translated into protein The flow of genetic information from DNA to RNA to Protein is called the CENTRAL DOGMA DNA Transcription RNA Translation Protein

  3. Chapter 12 Protein Synthesis (Overview) Central Dogma - FLOW IS FROM DNA TO RNA TO PROTEIN

  4. FLOW IS FROM DNA TO RNA TO PROTEIN Genes on DNA are expressed through proteins, which provide the molecular basis for inherited traits A particular gene, is a linear sequence of many nucleotides Specifies a polypeptide (long protein made of amino acids) Chapter 13 Protein Synthesis (Overview)

  5. Chapter 12 Protein Synthesis (Overview) Genes - discrete units of hereditary information comprised of a nucleotide sequence found in a DNA molecule.

  6. 12.1 RNA Three Types of RNA Messenger RNA (mRNA) – carries copies of genes (DNA) to the rest of the cell. Ribosomal RNA (rRNA) – make up the ribosomes. Transfer RNA (tRNA) – transfers the amino acids to the ribosomes as specified by the mRNA

  7. 12-1 Messenger (mRNA) Three main differences between mRNA and DNA Ribose instead of deoxyribose mRNA is single stranded mRNA has uracil in place of thymine (U instead of T)

  8. 12.1TRANSCRIPTION: The process of making mRNA from DNA Why do you need this process? Location of DNA? Nucleus Location of Ribosome? Cytoplasm mRNA takes code from DNA in the nucleus to the cytoplasm T A C T T C A A A A T C A T G A A G T T T T A G Strand to be transcribed DNA Transcription G U U U A G A U A A G U RNA Startcondon Stopcondon Translation Met Polypeptide Lys Phe

  9. Transcription produces genetic messages in the form of mRNA 12.1 In the nucleus, the DNA helix unzips And RNA polymerase lines up nucleotides along one strand of the DNA, following the base pairing rules As the single-stranded messenger RNA (mRNA) peels away from the gene The DNA strands rejoin RNA nucleotides RNA polymerase A C C A T T A U T C T G U G A C A U C C A C C A G A T T T A G G Direction of transcription Template Strand of DNA Newly made RNA

  10. 12.1 Eukaryotic mRNA is processed before leaving the nucleus Noncoding segments called introns are spliced out leaving only the coding exons A 5’ cap and a poly A tail are added to the ends of mRNA Cap and tail protect mRNA Exon Intron Exon Intron Exon DNA Transcription Addition of cap and tail Cap RNA transcript with cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence Nucleus Cytoplasm 5’ 3’

  11. A C C A T T A U T C G T U G A C A U C C A C C A G A T T T A G G Direction of transcription

  12. 12-3 Protein Synthesis - Translation • Translation is defined as going from mRNA to protein • tRNA which have amino acids attached are going to the ribosome in the cytoplasm. • What are amino acids? monomers of proteins • Does the order of amino acids matter? Yes, they must be in order for the protein to fold correctly. Amino acid attachment site

  13. How does the correct tRNA (with amino acid attached) bind to the mRNA? The tRNA contains an anticodon which matches up with the mRNA sequence (codon). Transfer RNA (tRNA) molecules serve as interpreters during translation 0 Amino acid attachment site Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Anticodon

  14. Ribosomes build polypeptides (proteins) A ribosome consists of two subunits Each made up of proteins and a kind of RNA called ribosomal RNA Translation at Ribosome tRNAmolecules Growingpolypeptide Largesubunit mRNA Small subunit 12.3 Translation

  15. The subunits of a ribosome Hold the tRNA and mRNA close together during translation 12.3 Translation Large ribosomalsubunit Met Met Initiator tRNA P site A site U C U A C A A U G AUG Startcodon Small ribosomalsubunit mRNA 1 2

  16. Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation Once initiation is complete amino acids are added one by one to the first amino acid The mRNA moves a codon at a time A tRNA with a complementary anticodon pairs with each codon, adding its amino acid to the peptide chain

  17. Figure out the exact sequence of amino acids needed • Take the DNA and transcribe it into mRNA • Example: TAC ATA CTA GCG ACT • mRNA: • Take the mRNA sequence and decode it using the codon chart. AUG UAU GAU CGC UGA AUG = MET UAU = TYR GAU = ASP CGC = ARG Animation

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