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12–3 RNA and Protein Synthesis 12-3 RNA and Protein Synthesis Slide 1 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Comparing The transcription process is similar to replication. •Transcription and replication both involve complex enzymes and complementary base pairing. •The two processes have different end results. – Replication copies all the DNA; transcription copies a gene. – Replication makes one copy; transcription can make many copies. Slide 2 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis 12–3 RNA and Protein Synthesis Genes are coded DNA instructions that control the production of proteins. Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA. RNA contains coded information for making proteins. Slide 3 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis 12–3 RNA and Protein Synthesis •RNA carries DNA’s instructions. •The central dogma states that information flows in one direction from DNA to RNA to proteins. Slide 4 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis 12–3 RNA and Protein Synthesis •The central dogma includes three processes. – Replication – Transcription – Translation •RNA is a link between DNA and proteins. Slide 5 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis The Structure of RNA The Structure of RNA There are three main differences between RNA and DNA: •The sugar in RNA is ribose instead of deoxyribose. •RNA is generally single-stranded instead of double stranded. •RNA contains uracil in place of thymine. Slide 6 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Types of RNA Types of RNA There are three main types of RNA: • messenger RNA • ribosomal RNA • transfer RNA Slide 7 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Types of RNA Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins. Slide 8 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Types of RNA Ribosome Ribosomal RNA Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made. Slide 9 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Types of RNA Amino acid Transfer RNA During protein construction, transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome. Slide 10 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Protein Synthesis DNA molecule DNA strand (template) 5 3 TRANSCRIPTION mRNA 5 3 Codon TRANSLATION Protein Slide 11 of 39 Amino acid End Show 12–3 RNA and Protein Synthesis Transcription Transcription 1. A transcription complex consisting of RNA and other proteins recognizes the start site of a gene and begins to unwind the DNA. 2. RNA polymerase reads one side of the DNA template and strings together a complementary strand of RNA nucleotides. Slide 12 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Transcription Transcription 3. The growing RNA strand hangs freely as it is transcribed and detaches completely once the entire gene is transcribed. 4. DNA Molecule 5. Nucleotides 6. Newly synthesized RNA strand 7. RNA polymerase Slide 13 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Transcription RNA RNA polymerase DNA Slide 14 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis The Genetic Code The Genetic Code The genetic code is the “common language” of mRNA instructions and is shared by almost all organisms. The code is written using four “letters” (the bases: A, U, C, and G). Slide 15 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis The Genetic Code A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid. •The start codon signals the start of translations and the amino acid methionine. •The stop codon is three codons that signal the end of a chain of amino acids. Slide 16 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis The Genetic Code Slide 17 of 39 Copyright Pearson Prentice Hall End Show The Genetic Code • The genetic code matches each codon to its amino acid or function. –three stop codons –one start codon, codes for methionine Slide 18 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Translation Translation Translation is the decoding of an mRNA message into a polypeptide chain (protein). –Ribosomes are the site of protein synthesis; made of rRNA and proteins –Catalyzes the formation of peptide bonds between amion acids During translation, the cell uses information from messenger RNA to produce proteins. Nucleus mRNA Copyright Pearson Prentice Hall Slide 19 of 39 End Show 12–3 RNA and Protein Synthesis Reading frame Codon • A reading frame is the series of 3 nonoverlapping nucleotides read, in order, by a cell. • 3 different reading frames are possible for each mRNA molecule. • Codons must be read in the correct reading frame for the correct protein to be made. Slide 20 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Anticodon Amino acids are linked to become a protein. • An anticodon is a set of three nucleotides that is complementary to an mRNA codon. • An anticodon is carried by a tRNA. • Transfer RNA (tRNA) is a type of RNA that carries amino acids from the cytoplasm to the ribosome. One end has a specific anticodon, the other end attaches to a specific amino acid. Slide 21 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Ribosomes Ribosomes consist of two subunits • The large subunit has three binding sites for tRNA. • The small subunit binds to mRNA. Slide 22 of 39 Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Translation Process 1. Ribosome assembles at the start codon; complementary tRNA molecule pair with the exposed codon. Lysine Phenylalanine tRNA Methionine Ribosome mRNA Slide 23 of 39 Start codon Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Translation 2. Protein Synthesis-ribosome helps bond the new amino acid to the start codon and breaks the bond between the amino acid and the first tRNA. Lysine tRNA Translation direction mRNA Ribosome Copyright Pearson Prentice Hall Slide 24 of 39 End Show 12–3 RNA and Protein Synthesis Translation 3. Ribosome pulls the RNA strand the length of one codon; first tRNA returns to the cytoplasm; another codon is exposed for tRNA binding. The process continues until the ribosome reaches Polypeptide a stop codon. Ribosome tRNA Slide 25 of 39 mRNA Copyright Pearson Prentice Hall End Show 12–3 RNA and Protein Synthesis Codon Genes and Proteins Codon Codon DNA Single strand of DNA mRNA Codon Codon Codon mRNA Protein Alanine Arginine Leucine Amino acids within a polypeptide Copyright Pearson Prentice Hall Slide 26 of 39 End Show 12–3 RNA and Protein Synthesis 1. Amino acid (Start codon methionine) 2. Polypeptide bond 3. Large subunit 4. tRNA 5. codons 6. Small subunit 7. mRNA 8. anticodon Slide 27 of 39 End Show 12–3 Click to Launch: Continue to: - or - Slide 28 of 39 End Show Copyright Pearson Prentice Hall 12–3 The role of a master plan in a building is similar to the role of which molecule? a. messenger RNA b. DNA c. transfer RNA d. ribosomal RNA Slide 29 of 39 End Show Copyright Pearson Prentice Hall 12–3 A base that is present in RNA but NOT in DNA is a. thymine. b. uracil. c. cytosine. d. adenine. Slide 30 of 39 End Show Copyright Pearson Prentice Hall 12–3 The nucleic acid responsible for bringing individual amino acids to the ribosome is a. transfer RNA. b. DNA. c. messenger RNA. d. ribosomal RNA. Slide 31 of 39 End Show Copyright Pearson Prentice Hall 12–3 A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the a. intron. b. exon. c. promoter. d. codon. Slide 32 of 39 End Show Copyright Pearson Prentice Hall 12–3 A codon typically carries sufficient information to specify a(an) a. single base pair in RNA. b. single amino acid. c. entire protein. d. single base pair in DNA. Slide 33 of 39 End Show Copyright Pearson Prentice Hall END OF SECTION