Dna notes GCSE


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Dna notes GCSE

  1. 1. WARM-UP #7
  2. 2. Exam style question: (extension)1) Why is DNA trapped so tightly inchromosomes?2) How are DNA proteins and traits related?
  3. 3. DNA(Deoxyribonucleic Acid)
  4. 4. Genetic material of cells…Genetic material of cells…• GENES – units of genetic material thatGENES – units of genetic material thatCODES FOR A SPECIFIC TRAITCODES FOR A SPECIFIC TRAIT• CalledCalled NUCLEIC ACIDSNUCLEIC ACIDS• DNA is made up of repeating moleculesDNA is made up of repeating moleculescalledcalled NUCLEOTIDESNUCLEOTIDES
  5. 5. DNA NucleotideDNA NucleotideOO=P-OOPhosphatePhosphateGroupGroupNNitrogenous baseNitrogenous base(A, G, C, or T)(A, G, C, or T)CH2OC1C4C3C25SugarSugar(deoxyribose)(deoxyribose)
  6. 6. A HISTORY OF DNAA HISTORY OF DNA• Discovery of the DNA double helixDNA double helixA. Frederick Griffith – Discovers that a factorin diseased bacteria can transform harmlessbacteria into deadly bacteria (1928)B. Rosalind Franklin - X-ray photo of DNA.(1952)C. Watson and Crick - described theDNA molecule from Franklin’s X-ray.(1953)SEE p. 292-293
  7. 7. Watson & Crick proposed…Watson & Crick proposed…•DNA had specific pairing between theDNA had specific pairing between thenitrogen bases:nitrogen bases:ADENINEADENINE –– THYMINETHYMINECYTOSINECYTOSINE -- GUANINEGUANINE•DNA was made ofDNA was made of 22 long stands oflong stands ofnucleotides arranged in a specific waynucleotides arranged in a specific waycalled thecalled the “Complementary Rule”“Complementary Rule”
  8. 8. DNA Double HelixDNA Double HelixNitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)““Rungs of ladder”Rungs of ladder”““Legs of ladder”Legs of ladder”Phosphate &Phosphate &Sugar BackboneSugar Backbone
  9. 9. DNA Double HelixDNA Double HelixPPPOOO123455335PPPOOO12 3455353G CT A
  10. 10. Nitrogenous BasesNitrogenous Bases• PURINESPURINES1. Adenine (A)Adenine (A)2. Guanine (G)Guanine (G)• PYRIMIDINESPYRIMIDINES3. Thymine (T)Thymine (T)4. Cytosine (C)Cytosine (C) T or CA or G
  11. 11. Chargaff’s RuleChargaff’s Rule• AdenineAdenine must pair with ThymineThymine• GuanineGuanine must pair with CytosineCytosine• Their amounts in a given DNA molecule will beabout the sameabout the same.G CT A
  13. 13. Genetic Diversity…Genetic Diversity…• DifferentDifferentarrangements ofarrangements ofNUCLEOTIDESNUCLEOTIDES in ain anucleic acid (DNA)nucleic acid (DNA)provides the key toprovides the key toDIVERSITYDIVERSITY amongamongliving organisms.living organisms.
  14. 14. The Code of Life…The Code of Life…• The “code” of the chromosome is theThe “code” of the chromosome is theSPECIFIC ORDERSPECIFIC ORDER that bases occur.that bases occur.A T C G T A T G C G G…A T C G T A T G C G G…
  15. 15. DNA is wrapped tightly aroundhistones and coiled tightly to formchromosomesSee p. 297
  16. 16. DNADNA ReplicationReplication• DNA must be copiedDNA must be copied• The DNA molecule producesThe DNA molecule produces 22IDENTICALIDENTICAL new complementarynew complementarystrands following the rules ofstrands following the rules ofbase pairing:base pairing:A-T, G-CA-T, G-C•Each strand of theEach strand of theoriginal DNA serves asoriginal DNA serves asa template for the newa template for the newstrandstrand See p. 298See p. 298
  17. 17. DNADNA ReplicationReplication• SemiconservativeSemiconservativeModel:Model:1. Watson and CrickWatson and Crickshowed:showed: the two strandsof the parental moleculeseparate, and eachfunctions as a templatefor synthesis of a newcomplementary strand.. Parental DNADNA TemplateNew DNA
  18. 18. 1. Why is replication necessary?2. When does replication occur?3. Describe how replication works.4. Use the complementary rule tocreate the complementarystrand:A---?G---?C---?T---?A---?G---?A---?G---?C---?A---?G---?T---?Replication Quiz
  19. 19. 1. Why is replication necessary?So both new cells will have the correctDNA2. When does replication occur?During interphase (S phase).3. Describe how replication works.Enzymes unzip DNA and complementarynucleotides join each original strand.4. Use the complementary rule tocreate the complementary strand:A---TG---CC---GT---AA---TG---CA---TG---CC---GA---TG---CT---AReplication Quiz
  20. 20. (1961)(1961) Watson & Crick proposed…Watson & Crick proposed…• ……DNA controlled cell function byDNA controlled cell function byserving as a template forserving as a template for PROTEINPROTEINstructure.structure.• 3 Nucleotides = a triplet or3 Nucleotides = a triplet or CODONCODON(which code for a specific AMINO ACID)(which code for a specific AMINO ACID)See p.303See p.303• AMINO ACIDSAMINO ACIDS are the building blocksare the building blocksof proteins.of proteins.
  21. 21. DNADNA TranscriptionTranscription• DNA can “unzip”DNA can “unzip”itself anditself and RNARNAnucleotides matchnucleotides matchup to the DNAup to the DNAstrand.strand.• Both DNA & RNABoth DNA & RNAare formed fromare formed fromNUCLEOTIDESNUCLEOTIDES andandare calledare called NUCLEICNUCLEICacids.acids.See p.301See p.301
  22. 22. DNADNA TranslationTranslation• The cell usesThe cell usesinformation frominformation from“messenger” RNA“messenger” RNAto produce proteinsto produce proteinsSee p.304-305See p.304-305We willWe willdiscuss detailsdiscuss detailsof this on aof this on alater datelater date
  23. 23. Transcription/Translation Quiz1. Why is transcription necessary?2. Describe transcription.3. Why is translation necessary?4. Describe translation.5. What are the main differencesbetween DNA and RNA.6. Using the chart on page 303,identify the amino acids coded for bythese codons:UGGCAGUGC
  24. 24. 1. Why is transcription necessary?Transcription makes messenger RNA(MRNA) to carry the code for proteins out ofthe nucleus to the ribosomes in thecytoplasm.2. Describe transcription.RNA polymerase binds to DNA, separates thestrands, then uses one strand as a templateto assemble MRNA.3. Why is translation necessary?Translation assures that the right amino acidsare joined together by peptides to form the
  25. 25. 4. Describe translation.The cell uses information from MRNA toproduce proteins.5. What are the main differences betweenDNA and RNA.DNA has deoxyribose, RNA has ribose;DNA has 2 strands, RNA has one strand;DNA has thymine, RNA has uracil.6. Using the chart on page 303, identify theamino acids coded for by these codons:UGGCAGUGCtryptophan-glutamine-cysteine
  26. 26. AMAZING DNA FACTS…AMAZING DNA FACTS…• DNA from a single humanDNA from a single humancell extends in a singlecell extends in a singlethread for almost 2 metersthread for almost 2 meterslong!!!long!!!• It contains informationIt contains informationequal to some 600,000equal to some 600,000printed pages of 500 wordsprinted pages of 500 wordseach!!!each!!!(a library of about 1,000 books)(a library of about 1,000 books)
  27. 27. LET’S REVIEW DNA…LET’S REVIEW DNA…1.1. List the conclusions Griffith & Avery,List the conclusions Griffith & Avery,Hershey & Chase drew from theirHershey & Chase drew from theirexperiments.experiments.2.2. Summarize the relationship betweenSummarize the relationship betweengenes & DNA.genes & DNA.3.3. Describe the overall structure of theDescribe the overall structure of theDNA molecule.DNA molecule.4.4. What are the 4 kinds of bases?What are the 4 kinds of bases?