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Structure and Function of DNA

Structure and Function of DNA. Ch. 13. DNA. Encodes hereditary information. Located in the nucleus of a eukaryotic cell. Each chromosome is a macromolecule of DNA. All living things have DNA and use the same code! Shape is double helix. Discovery of DNA. Early 1900s scientists knew

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Structure and Function of DNA

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  1. Structure and Function of DNA Ch. 13

  2. DNA • Encodes hereditary information. • Located in the nucleus of a eukaryotic cell. • Each chromosome is a macromolecule of DNA. • All living things have DNA and use the same code! • Shape is double helix.

  3. Discovery of DNA • Early 1900s scientists knew • chromosomes carry hereditary info • chromosomes made of DNA and protein But which substance was source of genetic info?

  4. Nucleotides • Subunits (monomers) of DNA = nucleotides • 3 parts of nucleotides: • Nitrogenous base • Phosphate group • sugar

  5. Four nitrogen bases: A,T,C,G Purines: Adenine Guanine Pyrimidines: Thymine Cytosine

  6. Base Pairs • Always A – T • Always C - G • Purines = double carbon rings • Pyrimidines = single carbon rings

  7. James Watson and Francis Crick • Watson (American) worked with Crick (English) at Cambridge, England to discover the double helical structure of DNA • Two outside strands of P and sugar • cytosine = guanine (3 bonds) • adenine = thymine (2 bonds) • Discovery of DNA Structure

  8. Maurice Wilkins and Rosalind Franklin Rosalind Franklin's contribution

  9. Double Helix • The sugar/phosphate make the backbone • Nitrogen bases are the rungs • Ladder twisted to form double helix http://www.biotechnologyonline.gov.au/images/contentpages/helix.jpg

  10. Order of the bases gives the code for proteins. http://newsimg.bbc.co.uk/media/images/38889000/gif/_38889947_dna_mouse2_203.gif

  11. Antiparallel- each side facing opposite direction

  12. DNA Visualizations DNA structure 3D structure of DNA Molecular Visualizations of DNA James Watson on DNA DNA Replication

  13. DNA Replication (S phase) http://classes.midlandstech.edu/carterp/Courses/bio225/chap08/08-03_DNAReplication_1.jpg

  14. DNA replication: Helicase enzyme uncoils DNA New complementary strand made, corresponds to bases on each original strand. (A-T) (C-G) Semiconservative = 1 new strand + 1 old See p. 301 in Holt textbook! http://www.contexo.info/DNA_Basics/images/dna_replicationHGPweb.gif

  15. DNA replication animation • DNA Replication visualization • DNA replication (6/10) • DNA replication short • DNA Replication • DNA replication Crash Course

  16. Protein Synthesis The Human Genome Overview of Protein Synthesis

  17. DNA http://www.biologie.uni-hamburg.de/b-online/library/bio201/trinity.gif

  18. Overview of protein synthesis http://www.scq.ubc.ca/wp-content/translation_01.gif

  19. Amino Acids: • Subunits of protein are called amino acids • Only 20 amino acids (a.a.) in all life • Amino acids link together make different proteins.

  20. Three bases code for 1 amino acid http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/graphics/GP.GeneticCode.GIF

  21. Compare DNA and RNA DNA RNA Deoxyribonucleic acid Ribonucleic acid Deoxyribose (sugar) ribose (sugar) A, C, G, T A, C, G, U (uracil) double stranded single stranded stays in nucleus can move out of the nucleus

  22. Three types of RNA: • Messenger RNA = mRNA • Transfer RNA = tRNA • Ribosomal RNA = rRNA

  23. Making proteins 1. DNA is transcribed into mRNA in nucleus (transcription) 2. mRNA leaves nucleus and bonds to rRNA on ribosome in cytoplasm. mRNA is then translated into proteins by ribosome. (translation) tRNA brings in amino acids to be bonded together to make protein.

  24. DNA transcription and protein synthesis

  25. Transcription • Copy DNA code into mRNA in nucleus. Uracil replaces thymine in RNA. (A-U) mRNA leaves nucleus and finds a ribosome in cytoplasm http://www.scientificpsychic.com/fitness/transcription.gif

  26. mRNA takes info to cytoplasm and bind to ribosome tRNA brings in amino acid & matches codon A.A. are linked to make protein. Translation https://eapbiofield.wikispaces.com/file/view/translation.gif

  27. Translation

  28. Codon = 3 letter mRNA code for one amino acid http://library.thinkquest.org/C0123260/basic%20knowledge/images/basic%20knowledge/RNA/genetic%20code.jpg

  29. DNA Visualizations Molecular Visualizations of DNA

  30. Overview of protein synthesis http://www.scq.ubc.ca/wp-content/translation_01.gif

  31. DNA – The original drawing Transcription RNA – Copies or blueprints Translation Amino Acid chain (protein) – the finished, functional product of a gene

  32. Central Dogma DNA  RNA  Proteins

  33. Gene Regulation: • Ability of organism to control which and when genes are expressed (translated)

  34. When things go wrong… • Are mutations heritable? • Are mutations beneficial/harmful/both? • Are mutations the cause of evolution? • What are mutations?

  35. Find the base pairs that are incorrect in this strand of DNA. G G A T A T T A C C G T T G A A A G C A T C C G A T G A T G C C A A C T G G C G C A

  36. Find the base pairs that are incorrect in this strand of DNA. G G A T A T T A C C G T T G A A A G C A T C C G A T G A T G C C A A C T G G C G C A ↑ ↑ ↑ ↑ ↑ ↑

  37. Genetic MUTATION A change in the nucleotide sequence of a gene. ACU vs. AGU

  38. SUBSTITUTION THE BIG FAT CAT ATE THE WET RAT THE BIZ FAT CAT ATE THE WET RAT

  39. Sickle Cell Single nucleotide substitution Ex: in sickle cell disease, valine is substituted for glutamate (GUA for GAA) http://carnegiescience.edu/first_light_case/horn/lessons/images/hemoglobins.GIF

  40. DELETION • THE BIG FAT CAT ATE THE WET RAT • THB IGF ATC ATA TET HEW ETR AT Ex: cystic fibrosis

  41. Cystic Fibrosis CTFR transmembrane protein Most common CF cause is deletion of 3 base pairs for phenyalanine http://www.largeglassdesign.com/nutrition/images/stories/cf/lung_affects.png

  42. Normal CFTR Sequence: Nucleotide ATC ATC TTT GGT GTT Amino Acid Ile Ile Phe Gly Val F508 CFTR Sequence: Nucleotide ATC ATT GGT GTT Amino Acid Ile Ile Gly Val

  43. INSERTION • THE BIG FAT CAT ATE THE WET RAT • THE BIG ZFA TCA TAT ETH EWE TRA Ex: Crohn’s disease

  44. FRAMESHIFT MUTATIONS • Insertion or deletion changes the reading frame: THE BIG FAT CAT ATE THE WET RAT THE BIG ZFA TCA TAT ETH EWE TRA T • Now you’re making a completely different amino acid sequence!

  45. DUPLICATION THE BIG FAT CAT ATE THE WET RAT THE BIG FAT FAT CAT ATE THE WET RAT

  46. MUTAGENS Substances like chemicals and radiation that can damage DNA

  47. Which mutations can be passed to offspring? Somatic or sex-cell mutations? Why?

  48. Chromosome mutations Pieces of DNA can be deleted or moved to a different location on the chromosome or to another chromosome.

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