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Protein Synthesis

Protein Synthesis. Chapter 8. A. What is protein synthesis?. 1. Also called gene expression 2. Central dogma of molecular biology: information flows from DNA  RNA  p roteins (Defined by Francis Crick) 3. So…a section of DNA ( gene ) is designed to create a specific protein.

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Protein Synthesis

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  1. Protein Synthesis Chapter 8

  2. A. What is protein synthesis? 1. Also called gene expression 2. Central dogma of molecular biology: information flows from DNA  RNA  proteins (Defined by Francis Crick) 3. So…a section of DNA (gene) is designed to create a specific protein

  3. B. RNA • What is RNA? a. Ribonucleic Acid b. Acts as a messenger between DNA and ribosomes c. Gives ribosomes instructions for making proteins

  4. 2. Structure of RNA a. Like DNA, made up of a long chain of nucleotides b. Unlike DNA, RNA is single stranded c. Nucleotide is different i. Phosphate is the same

  5. ii. Sugar – ribose (instead of deoxyribose in DNA) iii. Bases – adenine, cytosine, guanine and uracil (instead of thymine) - Cytosine-Guanine (C-G) - Adenine-Uracil (A-U)

  6. Structure of RNA

  7. C. Transcription – transfer of info from DNA to RNA (Look at page 227!) 1. Begins on one end of the gene – promoter/start signal 2. DNA molecule unzips 3. Free RNA nucleotides match up by base pairing 4. RNA molecule detaches and DNA molecule re-zips 5. Stops at end of gene – stop signal 6. Enzyme – RNA Polymerase

  8. 7. The RNA molecule formed is called messenger RNA (mRNA) a. Complementary to DNA; made in the nucleus b. Leaves the nucleus & goes to ribosome (in the cytoplasm) c. Contains the information needed for protein synthesis

  9. Transcription

  10. D. How is the genetic code used to make proteins? 1. Proteins are made by putting a string of amino acids (aa) together 2. There are 20 different amino acids

  11. 3. Different proteins are created by putting amino acids together in different sequences 4. RNA instructions are written in groups of three nucleotides called a codon 5. Each codon matches up with a specific amino acid (Look at page 230!)

  12. a. There may be more than one codon for an amino acid b. Promoter/Start codon: AUG (methionine) c. Stop codon: UAA, UAG and UGA

  13. E. Translation – using mRNA instructions to make proteins (Look at page 232!) 1. mRNA attaches to a ribosome 2. Transfer RNA (tRNA) brings amino acids over to the ribosome and matches up with the mRNA

  14. 3. Anticodons on tRNA molecules match up (base pairing) with the codons on the mRNA molecules 4. As the tRNA matches up with the mRNA (anti-codon to codon), a bond forms between the amino acids 5. Once the bond between amino acids forms, the tRNA releases the aa and leaves to find another aa

  15. Translation

  16. F. Regulation of Gene Expression 1. All cells within an organism have the exact same genes, but different types of cells express different combinations of genes 2. Genes can also be turned on & off a. Operator – turns a gene on b. Repressor – turns a gene off

  17. G. Gene Structure 1. Not all DNA contains information needed to make proteins 2. Introns – sections of a gene without coding information (not used to make proteins) 3. Exons – sections of a gene that do have information to make proteins “exons are expressed” 4. Before translation, the introns of mRNA are cut out, and the exons are spliced back together

  18. H. Mutations – changes in DNA 1. Move gene to a new location? a. Gene rearrangement b. New regulatory control  gene might be turned on when it should be turned off (or vice versa)

  19. 2. Change a gene? Gene alteration a. The amino acid sequence is affected b. Point Mutation – single nucleotide changes (ATG  AAG) (one amino acid affected) c. Frameshift Mutation – affects the whole gene (whole protein affected) i. Insertion (ATG  ATAG) ii. Deletion (ATG  AG)

  20. iii. Example of a frameshift mutation (caused by a deletion) The dog ate the cat. (Delete the d in “dog.”) The ogatethec at. After the deletion, the sentence (protein) doesn’t make sense!

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