DNA →RNA → PROTEINS Chapters 16 & 17

1. DNA→RNA → PROTEINSChapters 16 & 17 http://faculty.uca.edu/~johnc/mbi1440.htm http://www.wappingersschools.org/RCK/staff/teacherhp/johnson/visualvocab/mRNA.gif

2. 1928- GRIFFITH’s EXPERIMENT Scientists originally thought PROTEINS had to be the genetic material 12 A Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg

3. 1943- EXPERIMENTS BY OSWALD AVERY, MACLYN McCARTY, & COLIN MACLEOD WITH LIPIDS, POLYSACCHARIDES, OR PROTEINS THERE’S NO TRANSFORMATION ONLY NUCLEIC ACIDS CHANGE THE BACTERIA SO . . . NUCLEIC ACIDS CARRY THE INFORMATION ! http://www.synapses.co.uk/genetics/dnastruc.html

4. http://oceanworld.tamu.edu/resources/oceanography-book/Images/BacteriophageCartoon.jpghttp://oceanworld.tamu.edu/resources/oceanography-book/Images/BacteriophageCartoon.jpg 1952-Alfred Hershey and Martha Chase Bacteriophages are viruses that infect bacteria Phages are made of DNA surrounded by a protein coat http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg

5. HERSHEY CHASE BLENDER EXPERIMENT http://www.mun.ca/biology/scarr/hersheychase-experiment.jpg

6. ROSALIND FRANKLIN and MAURICE WILKINS Analyzed DNA with X-ray crystallography to try and determine structure of DNA 1953 - JAMES WATSON & FRANCIS CRICK used Rosalind Franklin’s X-ray crystallography images (PHOTO 51) to come up with alpha helix model for the structure of DNA http://en.wikipedia.org/wiki/Rosalind_Franklin http://www.time.com/time/time100/scientist/profile/watsoncrick.html

7. DOUBLE HELIX Linus Pauling's Triple helix model http://www.biosciences.bham.ac.uk/labs/minchin/tutorials/lgdna.html

8. Arrow from: http://www.harrythecat.com/graphics/b/arrow48d.gif STRUCTURE OF NUCLEIC ACIDS Built from NUCLEOTIDE SUBUNITS • NITROGEN BASES • CAN BE: • ADENINEGUANINECYTOSINETHYMINEURACIL Image by: Riedell Sugar can be DEOXYRIBOSE (DNA)RIBOSE (RNA)

9. DNA has no URACIL RNA has no THYMINE PURINES (A & G) have 2 RINGS PYRIMIDINES (T, C, & U) have 1 RING http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNA/fg4.html http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/fg29.html

10. Subunits come in as TRIPHOSPHATES Splitting of nucleotide triphosphates provides the energy to link the nucleotides See animation http://www.cat.cc.md.us/~gkaiser/biotutorials/energy/adpan.html

11. DNA • DOUBLE STRANDED • Strands run ANTIPARALLEL • Backbone = sugars and phosphates • Rungs of ladder = nitrogen bases • Hydrogen bonds hold sides of ladder together http://staff.jccc.net/pdecell/proteinsynthesis/antiparralell.gif

12. RNA • SINGLE STRANDED • Folds into 3D shape • Backbone = sugars and phosphates • Rungs of ladder = nitrogen bases http://tigger.uic.edu/classes/phys/phys461/phys450/ANJUM04/

13. 5’ and 3’ ENDS • 5’ and 3’ ends named for the CARBON

14. Erwin Chargaff analyzed DNA from different organisms and found CHARGAFF’s RULES: A = T G = C Now know its because: A always bonds with T G always bonds with C A Purine always bonds to a Pyrimidine

15. Semi- Conservative Conservative Dispersive

16. Images from: http://instruct1.cit.cornell.edu/courses/biog105/pages/demos/106/unit01/6.dnareplicationmodels.html MESELSON & STAHL Grew bacteria for many generations in radioactive (heavy) 15N . . . so all DNA is heavy Then grow in 14N, centrifuge as generations divide, and check to see where heavy DNA ends up http://www.sumanasinc.com/webcontent/animations/content/meselson.html

17. MESELSON & STAHL Can tell which model it is by the banding patterns of DNA molecules SO WHAT ? Proved SEMI-CONSERVATIVE REPLICATION MODEL http://www.sumanasinc.com/webcontent/animations/content/meselson.html

18. Chromosome Structure in Prokaryotes Approximately 5 million base pairs3,000 genes Chromosome E.coli bacterium Bases on the chromosome DNA molecule in bacteriasingle circular loop © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved

19. CENTRAL DOGMA OF MOLECULAR BIOLOGY(How information passes in cells) http://www.emunix.emich.edu/~rwinning/genetics/pics/dogma.jpg

20. http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/fg12.htmlhttp://student.ccbcmd.edu/~gkaiser/biotutorials/dna/fg12.html Starting place = ORIGIN OF REPLICATION Bacteria have one Eukaryotes-multiple spots DNA REPLICATION FORK

21. HOW NUCLEOTIDES ARE ADDED DURING DNA REPLICATION DNA REPLICATION FORK http://bio.usuhs.mil/biochem4.html

22. TELOMERES & TELOMERASE Image from: AP BIOLOGY by Campbell and Reese 7th edition Each replicationshortens DNA strand Primer removed but can’t be replaced with DNA because no 3’ end available for DNA POLYMERASE

23. TELOMERES-repetitive sequences added to ends of genes to protect information in code • TELOMERASE can add to telomere segments in cells that must divide frequently • Ex: Cells that give rise to sperm & eggs • Shortening of telomeres may play a role in aging • Cancer cells may have increased telomerase activity which allows them to keep dividing ANIMATION http://stemcells.nih.gov/info/scireport/appendixC.asp

24. PROOFREADING & REPAIR • Mistakes in final DNA: 1 in 10 billion • Mistakes in initial base pairing during replication: 1 in 100,000 • DNA POLYMERASE proofreads each base as it’s added & fixes errors • Errors can come from: 1. “proofreading mistakes” that are not caught 2. Environmental damage from CARCINOGENS (Ex: X-rays, UV light, cigarette smoke, etc)

25. NUCLEOTIDE EXCISION REPAIR • Cells continually monitor DNA and make repairs • NUCLEASES-DNA cutting enzyme removes errors • DNA POLYMERASE AND LIGASE can fill in gap and repair using other strand • Xeroderm pigmentosum- genetic disorder • mutation in DNA enzymes that repair UV damage in skin cells • can’t go out in sunlight • increased skin cancers/cataracts

26. DNA →RNATRANSCRIPTION

27. RNA- the Other Nucleic Acid Made of NUCLEOTIDES Sugar = ribose URACIL NOT THYMINE Single stranded http://tigger.uic.edu/classes/phys/phys461/phys450/ANJUM04 http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg

28. 3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS RIBOSOMAL RNA (rRNA) Made in nucleolus 2 subunits (large & small) Combine with proteins to form ribosomes Bacterial ribosomes differentsize than eukaryotic ribosomes • Evidence for ENDOSYMBIOTIC THEORY • Medically significant-some antibiotics targetbacterial ribosomes w/o harming host rRNA and t-RNA images from Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006 mRNA image from http://wps.prenhall.com/wps/media/tmp/labeling/1140654_dyn.gif

29. 3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS TRANSFER RNA (tRNA) ANTICODON sequence matches CODON on mRNA to add correct amino acids during protein synthesis AMINOACYL-tRNA SYNTHETASE Enzyme attaches a specific amino acid using energy from ATP http://www-math.mit.edu/~lippert/18.417/lectures/01_Intro/

30. 3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS MESSENGER RNA (mRNA) carries code from DNA to ribosomes

31. TRANSCRIPTION See a video clip aboutTRANSCRIPTION

32. Prokaryotes- mRNA functional as soon as transcribed • Eukarytoes-mRNA is processed before use SEE PROCESSING VIDEO Image from AP BIOLOBY by Campbell and Reese

33. mRNA’s require EDITING before use • Message in NOT CONTINUOUS • INTRONS are removed Image by Riedell

34. mRNA EDITING snRNPs (small nuclear ribonucleoproteins) Made of proteins and RNA Role in the SPLICEOSOME (Complex that cuts out the INTRONS and joins EXONS to make the final mRNA) RIBOZYMES-RNA molecules that function as enzymes (pre-RNA can remove its own introns)

35. INTRONS & EXONS • PROTEIN DOMAINS • Modular • Ex: • Active site, • site to attach to membrane • In many proteins, different exons code for different domains • May facilitate evolution of new proteins (EXON SHUFFLING) • Increased Crossing over • Mix & match exons Image from AP BIOLOGY by Campbell and Reese

36. GTP "cap" put on 5’ end- stability and used to bind mRNA to ribosome • PolyA "tail" put on 3’ end (AAA)- stability and movement through the nuclear membrane Image from AP BIOLOBY by Campbell and Reese

37. TRANSLATION(Protein synthesis)

38. 64 possible codons Code is REDUNDANT“WOBBLES” Some amino acidshave more than one codon. START=AUG(Methionine is 1st) 3 codons for STOP Section 12-3 Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006

39. http://www.biologycorner.com/bio4/notes/codon.html

40. Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006  Translation Section 12-3

41. Figure 12–18 Translation (continued) Section 12-3 Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006

42. TRANSLATION How translation works SEE ANOTHERTranslation Animation

43. REGULATION & MODIFICATION DURING TRANSCRIPTION • Proteins affect ability of RNA polymerase to bind to DNA AFTER TRANSCRIPTION • Speed of editing introns/exons • access to transport proteins or speed of transport out • Control amount of mRNA degradation by RIBONUCLEASES DURING TRANSLATION • Polyribosomes (polysomes) • Availability of enzymes • POST-TRANSLATIONAL MODIFICATION • Alter protein (add phosphates, sugars, etc) • Cut and join peptide chains

44. COMPLETING PROTEINS • POLYRIBOSOMES (POLYSOMES) • Numerous ribosomes translate same mRNA at same time • 3-D folding (1’, 2’, 3’ structure) • Chaparonins

45. POST-TRANSLATIONAL MODIFICATIONS • Some amino acids modified by addition ofsugars, lipids, phosphate groups, etc • Enzymes can modify ends, cleave into pieces join polypeptide strands (4’ structure) Ex: Made as proinsulin then cut Final insulin hormone made of two chains connected by disulfide bridges http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/insulin.html

46. 1st to suggest genes dictate phenotypes through enzymes that catalyze specific chemical reactions • Postulated that the symptoms of an inherited disease are due to inability to make a specific enzyme • Coined term “inborn errors of metabolism” to describe such diseases • Beginning of “One gene-one enzyme” hypothesis • ALCAPTONURIA- “black urine” disease- defect in enzyme that breaks down amino acid tyrosine ARCHIBALD GARROD 1902 http://www.personal.psu.edu/faculty/w/x/wxm15/Online/Molecular%20Biology/media/phenylalanine.gifhttp://www.nature.com/bjp/journal/v147/n1s/images/0706466f5.jpg

47. Mutations • Point mutations • single base change • base-pair substitution • silent mutation • no amino acid change • redundancy in code • missense • change amino acid • nonsense • change to stop codon Slide from Explore Biology by Kim Foglia

48. Point mutation leads to Sickle cell anemia What kind of mutation? Slide from Explore Biology by Kim Foglia

49. Sickle cell anemia Slide from Explore Biology by Kim Foglia

50. Mutations • Frameshift • shift in the reading frame • changes everything “downstream” • insertions • adding base(s) • deletions • losing base(s) • More damaging atbeginning of gene than at end Slide modified from: Explore Biology by Kim Foglia