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Chap. 12 DNA & RNA
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Chap. 12 DNA & RNA

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  1. Chap. 12DNA & RNA

  2. DNA - What is it? • It’s the molecule that makes- up the genetic code. • Polymer of double-stranded nucleotides

  3. Chromosome structure: (P. 297) • DNA + histones = chromatin • histones + chromatin = nucleosome • nucleosome allow lots of DNA to fit into a tiny space!! • Like a tape measure!

  4. Made of: • 1) deoxyribose sugar • 2) phosphate group • 3) Nitrogen base – which are • A)purines • Adenine & Guanine & • B)pyrimidines • Cytosine & Thymine

  5. The bases bond in a special arrangement. • A bonds with T • G bonds with C • These bonds are called complimentary bases. (At The Girl’s Club!!)

  6. Major functions of DNA: • Replication – “makin’ copies” & • Protein Synthesis – “tellin’ the cell what to do!”

  7. II. A. Replication • Process to make a copy of the DNA. Both strands of DNA act as a pattern for the new DNA strands.

  8. B. Steps: (inside the nucleus) • 1. Bonds between bases weakened & strands “unzip”.

  9. 2. The exposed bases bond with their complimentary bases found “floating” in the nucleus.

  10. 3. Sugar-phosphate bonds link. • This links the nucleotides together.

  11. III. A. How does this info (inside the nucleus) get outside to “boss” the cell around?” • By using….mRNA – messenger RNA • It takes the message outside to the ribosomes.

  12. B. What is RNA? • RibonucleicAcid • There are 3 types of RNA. • It controls the synthesis of proteins. • Polymer of single-stranded nucleotides

  13. C. Made of: 1) ribose (5 - C sugar) 2) the nitrogen base Uracil (replaces Thymine) 3) phosphate group

  14. D. Transcription – “Cross writing” • uses mRNA to write a message so the ribosomes understand “what to do”

  15. E. STEPS IN MAKING mRNA: 1) Enzymes separate DNA strands 2) Complimentary bases attach to exposed ends. “Uracil replaces Thymine”

  16. 3) Enzymes bond sugar- phosphates molecules • 4) Bonding continues until the end.

  17. 5) mRNA leaves the nucleus thru nuclear pores and enters cytoplasm.

  18. Nucleotides are “read” as a set of three called a codon. • Codons “carry” specific amino acids. • Certain codons mean start & others mean stop.

  19. For example… mRNA is UCGCACGGU codons are UCG – CAC – GGU P. 303 Fig. 12-17 – be able to identify the amino acids Amino acids are Serine – Histidine - Glycine

  20. QUICK LAB - P. 303 • RIGHT MARGIN • WRITE ANSWER IN ON A SEPARATE PAGE! • ANSWER #1 THRU #4 • A & C #1 ONLY

  21. IV. Translation – Interpreting the message to make proteins • Uses tRNA that float around in the cytoplasm.

  22. A. Made of: • An anticodon on one end - 3 nitrogen bases that bond to the codon, • And its specific amino acid on the other end.

  23. B. Steps in translation: • 1) mRNA connects to a ribosome at the start codon (AUG) • 2) ribosome “reads” the codon & identifies the anticodon. • (EX. codon AUG is with anticodon UAC)

  24. 3) rRNA (inside the ribosome) bonds the tRNA to its mRNA • 4) tRNA attaches its amino acid synthesizing specific proteins.

  25. 5) Peptide bonds unite the amino acids. • 6) This process continues until it reaches a stop codon

  26. The order of amino acids is very specific for proteins. • Enzymes, specific biomolecules…

  27. SO… • DNA has the “message” that is replicated for all new cells. • The message is sent out into the cells by transcription. • Proteins are assembled by translating the message.

  28. V. Mutations…. • … are “errors” in the messages • They could be harmful/lethal/ no affect

  29. Point mutations occur at one point in the DNA sequence. (P. 307) • Could be substitution, insertion or deletion of a nucleotide. • This is a frameshift mutation

  30. Chromosome mutations affect the entire chromosome • Could be deletion, inversion, duplication, or translocation

  31. More mutations: • Somatic cells mutations may affect only the individual • Sex cell mutations may affect offspring/children

  32. Figure Questions – P. 307 • 1. Describe what happened in the 1st box. • 2. What is the effect on the amino acid sequence? • 3. What happened in box 2? • 4. And the effect on the amino acid sequence?

  33. P. 308 Fig. 12-20 • What happened in: • Deletion… • Duplication… • Inversion… • Translocation…