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12.3 – RNA and Protein Synthesis
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Section Outline 12–3 RNA and Protein Synthesis A. The Structure of RNA
B. Types of RNA C. Transcription D. RNA Editing E. The Genetic Code F. Translation G. The Roles of RNA and DNA H. Genes and Proteins
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DNA Replication Section 12-2 Original strand DNA polymerase New strand
Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand
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RNA vs. DNA
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Bring amino acids to ribosome
Concept Map Section 12-3 RNA can be Messenger RNA Transfer RNA also called which functions to also called which functions to Bring amino acids to ribosome mRNA Carry instructions tRNA from to DNA Ribosome
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Transcription Section 12-3 RNA polymerase DNA RNA
Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA
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The Genetic Code Section 12-3 :
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Translation mRNA : Nucleus Messenger RNA mRNA Lysine Phenylalanine
Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon :
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Translation (continued)
The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome
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Protein Synthesis - Start to finish
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