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  1. DNA Chapter 10

  2. DNA • Holds our genetic information • Like a library • Important for mitosis to occur • Biologists had to discover the chemical nature of DNA to determine that it is responsible for our genetic information

  3. Griffith and Transformation • Transformation: when a strain of bacteria is changed by a gene or genes from another bacteria • Experiment • Inject mice with bacteria S.pneumoniae • Smooth colonies = virulent (disease causing) • Rough colonies = harmless bacteria

  4. Griffith and Transformation • If the virulent colonies were killed with heat & mixed with harmless bacteria, the harmless bacteria get transformed into virulent bacteria • Some factor of the harmless bacteria was transformed to become virulent

  5. Avery and DNA • Wanted to repeat Griffith’s experiment • Treated heat killed virulent bacteria with enzymes • Used two enzymes that destroyed proteins, and RNA • Another enzyme destroyed ONLY DNA (nucleic acids) Lethal Virus

  6. Avery and DNA Results • Results: bacteria treated with DNA destroying enzyme did not transform harmless bacteria into virulent bacteria • It must be the DNA that stores the genetic information from one generation to the next Lethal Virus Lethal Lethal Non Lethal

  7. Hershey-Chase • Bacteriophage: a virus that infects bacteria ONLY • Scientists wanted to see what gets injected into a bacteria to cause infection • Used a radioactive marker DNA and protein

  8. Hershey Chase Results • After infection, the bacteria that had radioactive marker on DNA showed that it is the DNA that is inserted into the bacteria • Results: geneticmaterial of the bacteriophage was DNA and not protein

  9. DNA Structure • Rosalind Franklin • Scientist that worked with X-raydiffraction • Used X-rays on a portion of DNA and the results showed an X pattern

  10. DNA Structure • Watson & Crick • Scientists that were able to figure out what Rosalind’s X-ray patternmeant • Result: DNA has a doublehelix pattern where the nitrogenous bases face each other in the middle

  11. DNA Structure • DNA has a double helix pattern • The sides of the ladder are the sugar and phosphate • Rungs of the ladder are the nitrogenousbases paired up • The bond between two nitrogenous bases is a hydrogen bond

  12. DNA Structure • Backbone of DNA is the sugar and phosphate • Nitrogenous bases stick out of side to form latter rungs • These bases are repeated in a pattern that form our genetic code

  13. DNA Structure • Monomer of DNA is a nucleotide • Phosphorous group • 5-carbon sugar • Nitrogenous base • 4 Nitrogenous bases in DNA • Adenine • Guanine • Thymine • Cytosine

  14. DNA Structure • Chargaff’s Rule • Scientist that discovered a peculiar trend between the 4 bases • Same percentage of Adenine as Thymine • Same percentage of Guanine as Cytosine • Adenine binds to Thymine • Guanine binds to Cytosine

  15. DNA Replication • Process by which DNA is copied in a cell before division • Each strand of DNA is needed to be a template for a new strand of DNA to be produced • Since you can use one strand to make the other side, they are said to be complementary

  16. Replicating DNA • Step 1: DNA molecules separates into two strands with help from enzyme named helicase • Breaks hydrogen bonds between bases • Creates a replicationfork

  17. Replicating DNA • Step 2: Enzyme named DNA polymeraseadds new nucleotides to other side of template strand • This forms new hydrogen bonds DNA Polymerase can only move in one direction (3’-5’) so you have one strand that leads and one that lags To join the gaps between lagging strands and enzyme (ligase) come and binds them

  18. Replicating DNA • Step 3: Once the DNA is replicated, the DNA polymerase releases

  19. How Replication Occurs • Enzymes help make new strands of DNA • Helicase “unzips” the DNA, separating the base pairs • DNApolymerase adds new bases to pair up with the template • This enzyme also proofreads to make sure everything matches • What would be the matching bases to the part of DNA shown below?

  20. Eukaryotes vs. Prokaryotes • Eukaryotes • Long rod shaped chromosomes • Replication starts in certain points on the chromosome • Try to be as effective and time efficient • Prokaryotes • Circular chromosome • Replication begins in one place • Ends once the DNA polymerase meets its starting point • Very fast

  21. Protein Synthesis • Two parts process to make a protein from a segment of DNA • Part one: Transcription • DNA RNA • Part two: Translation • RNA  Protein

  22. RNA • Made of nucleotides • Three differences between DNA & RNA • Sugar • DNA = deoxyribose sugar • RNA = ribose sugar • RNA is single stranded • RNA uses Uracil instead of Thymine to bond with Adenine

  23. RNA • Three types of RNA • mRNA • Messenger RNA • rRNA • Ribosomal RNA • tRNA • Transfer RNA

  24. RNA • Messenger RNA • This is a copy of complimentary strand of DNA • Eventually will code for a protein to be made

  25. RNA • Ribosomal RNA • RNA found in ribosomes (organelles in the cell)

  26. RNA • Transfer RNA • Help produce a protein from mRNA • Brings aminoacids (monomer of protein) to ribosome to bond them together and make a whole protein

  27. Transcription • Taking DNA and making an RNA copy • Step 1: RNApolymerase binds to a promoter and unwinds the strands • Step 2: RNA polymerase adds free RNA nucleotides that are complimentary to DNA strands • Once this is made it is called pre-mRNA • Step 3: RNA polymerase reaches a termination signal and releases

  28. RNA Editing • Pre-mRNA is a roughdraft to the final copy of mRNA • Some parts of pre-mRNA are not needed to make a certain protein • These unnecessary parts are called introns • Introns get cut out of pre-mRNA • Before leaving the nucleus, mRNA needs to get a 5’ cap and poly A tail to finalize the RNA strand

  29. The Genetic Code • Proteins are made of aminoacids • There are 20 amino acids • In order to make a protein from a strand of mRNA, the mRNA is read in a 3 letter sequence called codons

  30. The Genetic Code • Each three letter codon represents an amino acid • DNA = AGCGTGCCAATT • RNA = UCG-CAC-GGU-UAA • Amino acids = Ser-His-Gly-STOP

  31. The Genetic Code • Each three letter codon represents an amino acid • DNA = TACCGTCCGGTCATC • RNA = AUG-GCA-GGC-CAG-UAG • Amino acids = Met-Ala-Gly-Gln-STOP

  32. Translation • Taking mRNA and making a protein • Occurs in the cytoplasm on a ribosome • Step 1: 2 ribosomal subunits bind to mRNA and a tRNA molecule. The tRNA molecule matches to the codon of the mRNA sequence • The first amino acid is always Methionine • If mRNA = AUG, then tRNA = UAC • The tRNA has the anti-codon

  33. Translation • Step 2-3: As tRNA brings new aminoacids to the ribosome, past ones break off leaving just amino acids bonded to each other • Step 4: This continues until one of the three STOPcodons is met • Step 5: ribosomal units break down and the amino acid strand goes through proteinfolding

  34. Transcription & Translation • Clip

  35. The Human Genome • The entire genome sequence of a human • 3.2 billion base pairs in our 23 chromosomes • We now need to learn what each of these sequences code for • This will help with curing diseases and prevention of others