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DNA, RNA and Protein How the Information in DNA Is Used to Build a Protein Information Flow From DNA Replication (prior to nuclear division) Gene: sequence of DNA that codes for a protein DNA transcription RNA translation Protein (maintain cell metabolism and support growth) DNA and RNA Structure Primary Structure Secondary Structure DNA RNA Chain of nucleotides Double helix Chain of nucleotides Single folded chain Nucleotide = phosphate + sugar + nitrogen-containing base DNA and RNA Structure DNA Purine bases Pyrimidine bases 5-carbon sugar Adenine (A) Guanine (G) Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Cytosine (C) Uracil (U) deoxyribose ribose OH Phosphate RNA H PO4 OH PO4 OH Nucleotide Chain Nucleotides are joined together by dehydration synthesis The phosphate of one nucleotide is joined to sugar of next nucleotide, forming a “sugar-phosphate backbone” 3’ end A C G pairs with C T A A T G C A T 3’ end has free sugar G 5’ end has free phosphate •Two nucleotide chains •In opposite orientations •Held together by hydrogen bonds •Twisted into a helix T DNA Structure A pairs with T 5’ end Applying Your Knowledge In the DNA double helix, which base is paired with adenine? 1. Adenine 2. Cytosine 3. Guanine 4. Thymine 5. Uracil DNA Replication •DNA chains separate •Each chain is used as a pattern to produce a new chain •Each new DNA helix contains one “old” and one “new” chain DNA Replication DNA replication requires 1. Enzymes, including DNA polymerase that adds nucleotides in a 5’3’ direction. 2. nucleotides 3. energy 5’—A G C T — 3’ 3’— T C G A — 5’ 5’— A G C T— 3’ 3’—T C G A — 5’ Applying Your Knowledge 1. 2. 3. 4. Two new chains Two old chains One old and one new chain One helix has two new chains and one has two old chains 5. None of these is correct. After DNA replication, what is the composition of the new double-helical molecules? 5’ Building Your DNA Model 3’ Join the phosphate of one nucleotide to the sugar of the next one One chain can have bases in any order, the other chain must be complementary 3’ 5’ Your completed model will have two DNA chains, each with 9 nucleotides. Transcription = Production of RNA Using DNA as a Template •DNA chains separate •ONE DNA chain is used as a pattern to produce an RNA chain •RNA chain is released and the DNA chains reform the double-helix In DNA In RNA A U T A G C C G Transcription Transcription requires 1. Enzymes, including RNA polymerase that adds nucleotides in a 5’3’ direction. 2. nucleotides 3. energy 3’---TACAAAGAGACT---5’ 5’---ATG TTTCTC TGA---3’ 3’---TACAAA GAGACT---5’ DNA template 5’---AUGUUUCUCUGA---3’ mRNA 5’---ATG TTTCTC TGA---3’ Applying Your Knowledge What is the sequence of an RNA molecule transcribed from a DNA template strand that reads 3’-ATG-5’? 1. 5’-TAC-3’ 2. 5’-CAU-3’ 3. 5’-AUG-3’ 4. 5’-UAC-3’ 5. 3’-TAC-5’ Products of Transcription • Messenger RNA Contains the code words for the sequence of amino acids in a specific protein CODON = group of three nucleotides acting as a code word for an amino acid Products of Transcription • Transfer RNA “Translates” the message by bringing a specific amino acid into the correct position on the growing protein chain Has ANTICODON = a group of three nucleotides on a tRNA that recognizes a mRNA codon Has amino acid attachment site mRNA In mRNA In tRNA A U U A G C C G Genetic Code Chart is written as a CODON dictionary, reading 5’3’ Products of Transcription • Ribosomal RNA One of the structural components of the ribosome Ribosome = organelle where protein synthesis occurs Has sites to bind both mRNA and tRNA for tRNA for tRNA small ribosomal subunit mRNA binding site Applying Your Knowledge Which molecule contains the information for assembling the amino acids in the correct order in the protein? 1. rRNA 2. tRNA 3. mRNA 4. All of these 5. None of these 3’ Your completed messenger RNA will have 9 nucleotides. 5’ Read the template from 3’5’ to produce the mRNA from 5’3’ 5’ Building Your DNA Model 3’ Choose one DNA chain as the template for RNA Translation At the ribosome, codons in mRNA are recognized by tRNA anticodons to place amino acids in the specific sequence specified by the DNA. Three Stages of Translation: Initiation- assemble components to start process Elongation- add amino acids in repeated cycles Termination- release protein product Translation Initiation mRNA binds to ribosome First tRNA binds to mRNA met UAC 5’---AUGUUUCUCUGA---3’ mRNA Translation Elongation Next tRNA binds to mRNA met phe UACAAA 5’---AUGUUUCUCUGA---3’ mRNA Translation Elongation Amino acids are joined First tRNA is released UAC met phe AAA 5’---AUGUUUCUCUGA---3’ mRNA Translation Elongation Ribosome moves by one codon UAC met phe AAA 5’---AUGUUUCUCUGA---3’ mRNA Translation Elongation (second cycle) Next tRNA binds to mRNA UAC met phe leu AAA GAG 5’---AUGUUUCUCUGA---3’ mRNA Translation Elongation (second cycle) Amino acids are joined Second tRNA is released UAC met phe leu GAG 5’---AUGUUUCUCUGA---3’ mRNA AAA Translation Elongation (second cycle) Ribosome moves by one codon UAC met phe leu GAG 5’---AUGUUUCUCUGA---3’ mRNA AAA Translation Termination Termination factor binds to stop codon UAC met phe leu T GAG 5’---AUGUUUCUCUGA---3’ mRNA AAA Translation Termination Protein chain is released Other components separate met phe leu UAC T GAG AAA 5’---AUGUUUCUCUGA---3’ mRNA Applying Your Knowledge If the mRNA sequence for codons 5, 6, and 7 of a protein is 5’-AAG-AUU-GGA-3’, what is the amino acid sequence in the protein? 1. Gly-ile-lys 2. Arg-leu-glu 3. Glu-leu-arg 4. Asn-met-gly 5. Lys-ile-gly CODON Attach 3 bases to the tRNA to form the anticodon Building Your DNA Model Serine Read the CODON from 5’3’ to find the name of the amino acid Your completed model will have 3 tRNAs, one for each codon in mRNA. Show the name of the amino acid carried by each tRNA. Summary of Completed DNA Model • One DNA double helix, two chains of 9 nucleotides each – one chain can have any sequence – second chain must be complementary • One chain of mRNA, 9 nucleotides long – must be complementary to one of the two DNA chains (DNA template is 3’5’, mRNA is 5’3’) • Three tRNAs with appropriate amino acids attached – tRNA anticodons must match mRNA codons Functions of Nucleic Acids • DNA is the genetic material • RNA is an intermediary in protein synthesis • The nucleotide ATP is an energy carrier for cell activities Breakdown of ATP: Releasing Energy for Work Energetic ~P A P ~ P~ P ( ATP ) A ~P ( ADP ) P Synthesis of ATP: Storing Energy A ~P ( ADP ) P + energy + Pi (Inorganic Phosphate) A P ~ P~ P ( ATP )