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Chapter 13 RNA and Protein Synthesis Slide 2 DNA: The Blueprints The structure of DNA CUT the Pyramids Slide 3 DNA: The Blueprints The structure of DNA Double Helix #A = #T #C = #G Slide 4 Central Dogma of Biology DNA- blueprints; instructions mRNA- messenger that delivers the instructions Ribosome- factory that makes proteins tRNA- workers who build the proteins Proteins- ultimate product that all life is based on Slide 5 Ribosenucleic Acid (RNA) Slide 6 Transcription In the nucleus, enzymes make Messenger RNA (mRNA) copy of a portion of a DNA strand in a process called transcription. mRNA takes the information from DNA and moves it to the cytoplasm Made be the enzyme RNA polymerase which starts at a promoter (section of DNA) Slide 7 RNA Processing Only in eukaryotic cell mRNA be edited before use Introns- sections to be removed Introns are in the way Exons- expressed mRNA Slide 8 What is the mRNA sequence? DNA is always read from 3 5 Slide 9 The Genetic Code Translation- changing mRNA into an amino acids chain (protein) called a polypeptide A group of three nitrogenous bases in mRNA code for one amino acid. Each group is known as a codon There are 20 Amino Acids How do we know a codon is 3 bases long? Slide 10 Codons How many different DNA bases are there? -4 (A, T, C, G) How many mRNA bases are there? -4 (A, U, C, G) If a codon was only 1 base long how many amino acids could you have? -Only 4 (A= AA #1, U= AA #2, C= AA #3, G = AA #4) If a codon was 2 bases long how many amino acids could you have? -4 2 = 16 (AA, AU, AC, AG, UU, UA, UC, UG, CC,CA, CU, CG, GG, GA, GU, GC) Since there are 20 Amino Acids, a codon must be 3 bases 4 3 =64 Multiple codons mean the same Amino acid Slide 11 Code is degenerate (reused) Slide 12 What is the AA sequence? Codons to remember: Start codon- AUG All proteins start with Methoinine Stop Codons- UAA, UAG, UGA Slide 13 Translation: From mRNA to Protein Translating the mRNA code: 1) Need Ribosomal RNA (rRNA) Slide 14 Translation: From mRNA to Protein 2) Need Transfer RNA (tRNA) -anticodon on tRNA pairs with codons in mRNA Slide 15 Translation: From mRNA to Protein 1) tRNA bring Methionine to A-site 2) Ribosome moves to next condon 3) tRNA brings AA#2 to A-site AA in P-site (Methionine) binds to AA#2 4) Ribosome moves to next codon 5) tRNA brings AA#3 to A-site AA in P-site binds to AA in A-site tRNA in E-site is released 6) Repeat 2-5 until Ribosome hits a stop codon 7) Ribosome releases mRNA and AA chain. Slide 16 Inside prokaryotes transcription and translation happen at the same time. Why is this possible? Prokaryotes have no nucleus Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Mutations Any change in the DNA sequence is called a mutation. Mutations can be caused by errors in replication, transcription, cell division, or by external agents. Slide 22 Mutations A point mutation is a change in a single base pair in DNA. A point mutation in the base pairs of a codon can change an amino acid A mutation in the 3 rd base is saver than the 1 st. 64 codons and only 20 AA. Extra codons used to protect against mutation Slide 23 Slide 24 Slide 25 Mutations A mutation in which a single base is added to or deleted from DNA is called a frameshift mutation Slide 26 Chromosomal Alterations Structural changes in chromosomes are called chromosomal mutations. Slide 27 Causes of Mutations Any agent that can cause a change in DNA is called a mutagen Radiation X rays, cosmic rays, ultraviolet light, and nuclear radiation Chemicals dioxins, asbestos, benzene, and formaldehyde High temperatures Slide 28 Slide 29 Slide 30 Thats all