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Chapter 12: DNA, RNA, AND PROTEIN SYNTHESIS

Chapter 12: DNA, RNA, AND PROTEIN SYNTHESIS. Proteins Are Made by Decoding Information in DNA. Proteins have many different functions in the body Hemoglobin (transports oxygen) Keratin (part of hair) Enzymes Proteins are not made directly from DNA because it can not leave the nucleus

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Chapter 12: DNA, RNA, AND PROTEIN SYNTHESIS

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  1. Chapter 12: DNA, RNA, AND PROTEIN SYNTHESIS

  2. Proteins Are Made by Decoding Information in DNA • Proteins have many different functions in the body • Hemoglobin (transports oxygen) • Keratin (part of hair) • Enzymes • Proteins are not made directly from DNA because it can not leave the nucleus • Another molecule is involved…

  3. Ribonucleic Acid (RNA) • RNA is a nucleic acid like DNA, BUT… • It’s a single strand of nucleotides • It contains ribose instead of deoxyribose • It contains the base Uracil (U) instead of Thymine (T)

  4. Read page 336 in your book and create a Venn Diagram comparing and contrasting DNA and RNA…

  5. Protein Synthesis Steps: • Transcription • Translation

  6. Transcription • DNA can not leave the nucleus so a messenger is needed to get the information to the rest of the cell • Transcription is the process of making a molecule of RNA (messenger) from a molecule of DNA • Like writing notes on another piece of paper from information on this powerpoint

  7. Transcription • The enzyme RNA polymerase binds to a segment of DNA and “unzips” DNA similar to replication • RNA nucleotides assemble themselves to match up with the bases on DNA • This continues until a “stop” signal is reached

  8. Transcription 4. When transcription is complete, the DNA “zips” back up and the new mRNA (m = messenger) is released. 5. The new mRNA travels out of the nucleus to the cytoplasm and attaches to a ribosome

  9. Practice Write the complementary base sequence of the RNA molecule using DNA as a template. DNA =TAC ACC TTG AAG GGA CCC AGC CGC TTC ACT

  10. Answer: AUG UGG AAC UUC CCU GGG UCG GCG AAG UGA * Note Uracil(U) replaces Thymine (T) in RNA

  11. Translation • Translation is the process of making a protein from the information on the mRNA strand • Translation switches from the RNA “language” to the protein “language” • DNA base sequence is thereby “decoded”

  12. Translation • A ribosome attaches to the mRNA made during transcription. • The ribosome will read a 3-letter base sequence called a codon on the mRNA molecule. • Each codon on the mRNA codes for a specific amino acid (monomer of proteins)

  13. Translation • As the ribosome translates each codon, a molecule of tRNA (t = transfer) brings the complimentary anti-codon to the ribosome. • Each molecule of tRNA has the correct amino acid that is needed to complete the protein. 6. The codon on the mRNA and the anti-codon on the tRNA bond putting the amino acid into place.

  14. Translation • As the ribosome continues to translate the mRNA, a protein is simultaneously made. • Each amino acid is bonded to the next by a peptide bond forming the finished protein. • The finished protein is released when a stop codon is reached

  15. Practice Using the molecule of mRNA in your notes, write the corresponding tRNA

  16. Answers tRNA: UAC ACC UUG AAG GGA CCC AGC CGC UUC ACU

  17. Find the corresponding amino acids for each codon. *Use the codon chart in your notes…

  18. Answers Amino Acids: (start) tryptophan – asparagine – phenylalanine – proline – glycine – serine – alanine – lysine (stop)

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