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DNA Function

DNA Function. genetic information how to build/grow, operate, and repair cells Specifically how and when to make proteins passed from one cell generation to the next; From one cell to the next within an individual passed from parent to child. DNA Organization.

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DNA Function

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  1. DNA Function • genetic information • how to build/grow, operate, and repair cells • Specifically how and when to make proteins • passed from one cell generation to the next; • From one cell to the next within an individual • passed from parent to child

  2. DNA Organization • DNA molecule = genes + regulatory DNA + “other” • gene =protein instructions • 20-25k estimated genes (but >100,000 estimated proteins….problem…..) • regulatory= when to activate gene/make a protein “chromosome” ~3% of DNA non-coding: ~97% of DNA

  3. DNA Structure • long chains of nucleotides • Nucleotide = sugar + phosphate + nitrogenous base • Sugar = deoxyribose (5C) • 4 Different Bases: A, T, G, C • Bases = pyrimidines (1 ring) or purines (2 rings)

  4. DNA Structure Cont.:Double Helix double stranded Sugars bonded to phosphate  “backbone” Covalent bonds Base bonded to base Hydrogen bond Twisted=helix 5’ 5’ 3’ 3’ hydrogen bond covalent bond ‘f’-five; ‘f’ phosphate; 5’ end

  5. DNA Structure Cont.:Complementary Base Pairing • 4 different bases • Complementary pairing • C—G • A—T

  6. Functional Characteristics of DNA: IMPORTANT!! Information = order of the bases/base sequence ATTGCGCA means something different then: ATTGCGGA Complementary base pairing allows: DNA to be copied over and over and the information stays the same. information to be transferred to mRNA and stay the same

  7. Importance of base-pairing, information is preserved A T T C G C G A T A T T C G C G A T T A A G C G C T A A T T C G C G A T T A A G C G C T A A T T C G C G A T T A A G C G C T A T A A G C G C T A A T T C G C G A T Strands copies: result is two strands identical to each other and original strands Strands separate for copying Single strand Double strand

  8. mRNA • A temporary copy of a gene’s protein assembly instructions • Single stranded chains of nucleotides • Sugar = ribose • Bases and Pairing • G, C, A, U replaces T • G-C • T-A or A-U • Codons = 3-base groups • One codon is a “start” codon • Three codons are “stop codons” • Each codon corresponds to a specific amino acid (except stops)

  9. tRNA Amino acids • Single stranded piece of RNA • Carried and delivers amino acids • Anticodon binds w/ mRNA codon 3-44

  10. Protein Synthesis: making proteins from DNA • Transcription= DNA  mRNA • (in nucleus) • Translation = mRNA  Protein • (in cytoplasm @ ribosome)

  11. Transcription:from DNA  mRNA • promoter = how much transcription • RNA Polymerase unzips gene and moves down DNA • Complimentary RNA nucleotides bind DNA • RNA nucleotides bind together (via RNA poly) • at end of gene mRNA detaches and RNA poly detaches • DNA zips up when transcription is done • mRNA is made and leaves nucleus and enters cytoplasm 3-35

  12. Transcription mRNA being created RNA Polymerase Unzipped DNA (gene) Coding strand 3-36

  13. Transcription

  14. Translation • In cytoplasm mRNA combines with a ribosome • tRNA carrying amino acids bind the mRNA codons based on complementary pairing between codon and anticodon • tRNA deliver the amino acids to ribosome • Amino acids (delivered by tRNA) bind together to begin forming protein • Repeat steps 2-4 until end of mRNA is reached and completed protein is made • See following two slides for additional explaination

  15. Translation, part 1

  16. Translation, part 2

  17. Examples: Codon GAC corresponds to amino acid Asp Codon CAG corresponds to amino acid Gln

  18. DNA  mRNA  Proteins  cell function/structure Genetic Expression: from DNA to cell function/structure This is the big picture: The instructions on DNA make proteins when the cell receives a signal and then those proteins are synthesized and used as enzymes, transport proteins, receptors, hormones or as building materials for the cell so that the cell can carry out its functions • structure • transport • contraction • receptors • cell ID • hormones/signaling

  19. Protein Synthesis and the Genetic Code DNA template strand 3-43

  20. Mutations, DNA, and Protiens • Mutation = change in DNA base sequence • change in protien  change in structure and/or function Change DNA sequence Change mRNA sequence Change amino acid sequence Change protein function or make non-functional Change protein Change codons

  21. Restriction Enzymes: Restriction enzyme cuts when it encounters: CGGC GCCG • Discovered in bacteria • Cut DNA at specific locations A T C G G C C A T T C T A G C C G G T A A G A T C T A G C C A T C G G C C A T T C T A G C C G G T A A G G G C C A T T C Result is one piece of dna cut into two fragments (one shorter, one longer) due to restriction enzymes G G T A A G

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