Copyright © 2006 Pearson Prentice Hall, Inc. Chapter 9 Gene Expression and Regulation
Copyright © 2006 Pearson Prentice Hall, Inc. 9.1 How Is the Information in DNA Used in a Cell? Most Genes Contain Information for the Synthesis of a Single Protein RNA Intermediaries Carry the Genetic Information for Protein Synthesis –Table 9.1 A Comparison of DNA and RNA (p. 126)
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9.1 How Is the Information in DNA Used in a Cell? Overview: Genetic Information Is Transcribed into RNA, Then Translated into Protein –Figure 9.1 Genetic information flows from DNA to RNA to protein (p. 126)
Copyright © 2006 Pearson Prentice Hall, Inc. DNA messenger RNA protein ribosome (a) Transcription (cytoplasm) (nucleus) gene (b) Translation
Copyright © 2006 Pearson Prentice Hall, Inc. 9.2 What Is the Genetic Code? A Sequence of Three Bases Codes for an Amino Acid –Table 9.2 The Genetic Code (Codons of mRNA) (p. 127)
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9.3 How Is the Information in a Gene Transcribed into RNA? Transcription Begins When RNA Polymerase Binds to the Promoter of a Gene –Figure 9.2 Transcription is the synthesis of RNA from instructions in DNA (p. 128)
Copyright © 2006 Pearson Prentice Hall, Inc. RNADNA template strand promote r termination signal Initiation Elongation Termination Conclusion of transcription gene 1gene 2 gene 3 DNA At the end of a gene, RNA polymerase encounters a sequence of DNA called a termination signal. RNA polymerase detaches from the DNA and releases the RNA molecule. RNA polymerase travels along the DNA template strand, catalyzing the addition of ribose nucleotides into an RNA molecule. The nucleotides in the RNA are complementary to the template strand of the DNA. RNA polymerase binds to the promoter region of DNA near the beginning of a gene, separating the double helix near the promoter. After termination, the DNA completely rewinds into a double helix. The RNA molecule is free to move from the nucleus to the cytoplasm for translation, and RNA polymerase may move to another gene and begin transcription once again. DNA RNA polymerase
Copyright © 2006 Pearson Prentice Hall, Inc. promoter Initiation gene 1gene 2 gene 3 DNA RNA polymerase binds to the promoter region of DNA near the beginning of a gene, separating the double helix near the promoter. DNA RNA polymerase
Copyright © 2006 Pearson Prentice Hall, Inc. RNADNA template strand Elongation RNA polymerase travels along the DNA template strand, catalyzing the addition of ribose nucleotides into an RNA molecule. The nucleotides in the RNA are complementary to the template strand of the DNA.
Copyright © 2006 Pearson Prentice Hall, Inc. termination signal Termination At the end of a gene, RNA polymerase encounters a sequence of DNA called a termination signal. RNA polymerase detaches from the DNA and releases the RNA molecule.
Copyright © 2006 Pearson Prentice Hall, Inc. Conclusion of transcription After termination, the DNA completely rewinds into a double helix. The RNA molecule is free to move from the nucleus to the cytoplasm for translation, and RNA polymerase may move to another gene and begin transcription once again. RNA
Copyright © 2006 Pearson Prentice Hall, Inc. 9.3 How Is the Information in a Gene Transcribed into RNA? Elongation Generates a Growing Strand of RNA –Figure 9.3 RNA transcription in action (p. 129)
Copyright © 2006 Pearson Prentice Hall, Inc. gene DNA RNA molecules RNA transcription
Copyright © 2006 Pearson Prentice Hall, Inc. 9.3 How Is the Information in a Gene Transcribed into RNA? Transcription Stops When RNA Polymerase Reaches the Termination Signal Transcription Is Selective
Copyright © 2006 Pearson Prentice Hall, Inc. 9.4 What Are the Functions of RNA? Figure 9.4 Cells synthesize three major types of RNA (p. 130)
Copyright © 2006 Pearson Prentice Hall, Inc. Ribosome: contains ribosomal RNA (rRNA) Transfer RNA (tRNA) large subunit tRNA/amino acid binding sites catalytic site attached amino acid anticodon small subunit tyr Messenger RNA (mRNA)
Copyright © 2006 Pearson Prentice Hall, Inc. Messenger RNA (mRNA)
Copyright © 2006 Pearson Prentice Hall, Inc. Ribosome: contains ribosomal RNA (rRNA) large subunit tRNA/amino acid binding sites catalytic site small subunit
Copyright © 2006 Pearson Prentice Hall, Inc. Transfer RNA (tRNA) attached amino acid anticodon tyr
Copyright © 2006 Pearson Prentice Hall, Inc. 9.4 What Are the Functions of RNA? Messenger RNA Carries the Code for a Protein from the Nucleus to the Cytoplasm Ribosomal RNA and Proteins Form Ribosomes Transfer RNA Molecules Carry Amino Acids to the Ribosomes
Copyright © 2006 Pearson Prentice Hall, Inc. 9.5 How Is the Information in Messenger RNA Translated into Protein? Translation Begins When tRNA and mRNA Bind to a Ribosome –Figure 9.5 Translation is the process of protein synthesis (p. 132)
Copyright © 2006 Pearson Prentice Hall, Inc. Elongation: Initiation: Termination: The third codon of mRNA (CAU) base-pairs with the anticodon (GUA) of a tRNA carrying the amino acid histidine (his). This tRNA enters the second tRNA binding site on the large subunit. The catalytic site forms a new peptide bond between valine and histidine. A three-amino- acid chain is now attached to the tRNA in the second binding site. The tRNA in the first site leaves, and the ribosome moves one codon over on the mRNA. This process repeats until a stop codon is reached; the mRNA and the completed peptide are released from the ribosome, and the subunits separate. stop codon completed peptide catalytic site The second codon of mRNA (GUU) base-pairs with the anticodon (CAA) of a second tRNA carrying the amino acid valine (val). This tRNA binds to the second tRNA site on the large subunit. The catalytic site on the large subunit catalyzes the formation of a peptide bond linking the amino acids methionine and valine. The two amino acids are now attached to the tRNA in the second binding position. The "empty" tRNA is released and the ribosome moves down the mRNA, one codon to the right. The tRNA that is attached to the two amino acids is now in the first tRNA binding site and the second tRNA binding site is empty. ribosome moves one codon to right catalytic site initiator tRNA detaches peptide bond catalytic site met val his arg The large ribosomal subunit binds to the small subunit. The methionine tRNA binds to the first tRNA site on the large subunit. The initiation complex binds to an mRNA molecule. The methionine (met) tRNA anticodon (UAC) base- pairs with the start codon (AUG) of the mRNA. A tRNA with an attached methionine amino acid binds to a small ribosomal subunit, forming an initiation complex. initiation complex amino acid methionine tRNA small ribosomal subunit mRNA tRNA catalytic site first tRNA binding site second tRNA binding site large ribosomal subunit met val his val ile arg val
Copyright © 2006 Pearson Prentice Hall, Inc. Initiation: The large ribosomal subunit binds to the small subunit. The methionine tRNA binds to the first tRNA site on the large subunit. The initiation complex binds to an mRNA molecule. The methionine (met) tRNA anticodon (UAC) base- pairs with the start codon (AUG) of the mRNA. A tRNA with an attached methionine amino acid binds to a small ribosomal subunit, forming an initiation complex. initiation complex amino acid methionine tRNA small ribosomal subunit mRNA tRNA catalytic site first tRNA binding site second tRNA binding site large ribosomal subunit met
Copyright © 2006 Pearson Prentice Hall, Inc. A tRNA with an attached methionine amino acid binds to a small ribosomal subunit, forming an initiation complex. initiation complex amino acid methionine tRNA small ribosomal subunit met
Copyright © 2006 Pearson Prentice Hall, Inc. The initiation complex binds to an mRNA molecule. The methionine (met) tRNA anticodon (UAC) base- pairs with the start codon (AUG) of the mRNA. mRNA tRNA met
Copyright © 2006 Pearson Prentice Hall, Inc. The large ribosomal subunit binds to the small subunit. The methionine tRNA binds to the first tRNA site on the large subunit. catalytic site first tRNA binding site second tRNA binding site large ribosomal subunit met
Copyright © 2006 Pearson Prentice Hall, Inc. Elongation: The second codon of mRNA (GUU) base-pairs with the anticodon (CAA) of a second tRNA carrying the amino acid valine (val). This tRNA binds to the second tRNA site on the large subunit. The catalytic site on the large subunit catalyzes the formation of a peptide bond linking the amino acids methionine and valine. The two amino acids are now attached to the tRNA in the second binding position. The "empty" tRNA is released and the ribosome moves down the mRNA, one codon to the right. The tRNA that is attached to the two amino acids is now in the first tRNA binding site and the second tRNA binding site is empty. ribosome moves one codon to right catalytic site initiator tRNA detaches peptide bond catalytic site met val met val
Copyright © 2006 Pearson Prentice Hall, Inc. The second codon of mRNA (GUU) base-pairs with the anticodon (CAA) of a second tRNA carrying the amino acid valine (val). This tRNA binds to the second tRNA site on the large subunit. catalytic site met val
Copyright © 2006 Pearson Prentice Hall, Inc. The catalytic site on the large subunit catalyzes the formation of a peptide bond linking the amino acids methionine and valine. The two amino acids are now attached to the tRNA in the second binding position. peptide bond val met
Copyright © 2006 Pearson Prentice Hall, Inc. The "empty" tRNA is released and the ribosome moves down the mRNA, one codon to the right. The tRNA that is attached to the two amino acids is now in the first tRNA binding site and the second tRNA binding site is empty. ribosome moves one codon to right catalytic site initiator tRNA detaches met val
Copyright © 2006 Pearson Prentice Hall, Inc. Termination: The third codon of mRNA (CAU) base-pairs with the anticodon (GUA) of a tRNA carrying the amino acid histidine (his). This tRNA enters the second tRNA binding site on the large subunit. The catalytic site forms a new peptide bond between valine and histidine. A three-amino- acid chain is now attached to the tRNA in the second binding site. The tRNA in the first site leaves, and the ribosome moves one codon over on the mRNA. This process repeats until a stop codon is reached; the mRNA and the completed peptide are released from the ribosome, and the subunits separate. stop codon completed peptide catalytic site his arg met val his val ile arg val
Copyright © 2006 Pearson Prentice Hall, Inc. The third codon of mRNA (CAU) base-pairs with the anticodon (GUA) of a tRNA carrying the amino acid histidine (his). This tRNA enters the second tRNA binding site on the large subunit. catalytic site his met val
Copyright © 2006 Pearson Prentice Hall, Inc. The catalytic site forms a new peptide bond between valine and histidine. A three-amino- acid chain is now attached to the tRNA in the second binding site. The tRNA in the first site leaves, and the ribosome moves one codon over on the mRNA. met his val
Copyright © 2006 Pearson Prentice Hall, Inc. This process repeats until a stop codon is reached; the mRNA and the completed peptide are released from the ribosome, and the subunits separate. stop codon completed peptide arg met his val ile arg
Copyright © 2006 Pearson Prentice Hall, Inc. 9.5 How Is the Information in Messenger RNA Translated into Protein? Elongation Generates a Growing Chain of Amino Acids A Stop Codon Signals Termination –Figure 9.6 Complementary base pairing is critical to decoding genetic information (p. 133)
Copyright © 2006 Pearson Prentice Hall, Inc. template DNA strand complementary DNA strand DNA gene codons anticodons amino acids etc. mRNA tRNA methionineglycinevaline protein etc.
Copyright © 2006 Pearson Prentice Hall, Inc. template DNA strand complementary DNA strand DNA gene etc.
Copyright © 2006 Pearson Prentice Hall, Inc. codons etc. mRNA
Copyright © 2006 Pearson Prentice Hall, Inc. etc. tRNA
Copyright © 2006 Pearson Prentice Hall, Inc. amino acids etc.methionineglycinevaline protein