1. DNA Chapter 12

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 containing virus for pneumonia  Smooth colonies = have bacterial infection  Rough colonies = harmless bacteria

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

5. Avery and DNA  Wanted to repeat Griffith’s experiment  Treated heat-killed virulent bacteria with enzymes  One enzyme destroyed RNA and proteins  Another enzyme destroyed ONLY DNA Lethal Virus

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

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 for DNA and protein

8. Hershey Chase  After infection, the bacteria that had radioactive marker on DNA showed that it is the DNA that is inserted into the bacteria  Results: DNA from the virus is what causes infection

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

10. 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

11. DNA Structure  Chargaff’s Rule  Scientist that discovered a pattern between the 4 bases  Same percentage of Adenine as Thymine  Same percentage of Guanine as Cytosine  Scientists still not sure how they match up though

12. DNA Structure  Rosalind Franklin  Scientist that worked with X-ray diffraction  Used X-rays on a portion of DNA and the results showed an X pattern

13. DNA Structure  Watson & Crick  Scientists that were able to understand Rosalind’s X-ray picture  Result: DNA has a double helix pattern where the nitrogenous bases face each other

14. DNA Structure  DNA has a double helix pattern  Looks like a ladder twisted up  The sides of the ladder are the sugar and phosphate and the rungs of the ladder are the nitrogenous bases paired up  The adenine binds to thymine  The guanine binds to cytosine  This concluded Chargaffs’s rule  base pairing

15. DNA and Chromosomes  Prokaryotes  Lack nucleus and organelles  DNA floats as a circle in the cytoplasm  Eukaryotes  1000 times more DNA than prokaryotes  DNA is located in nucleus  Specific number of chromosomes  Ex: Humans have 46 chromosomes

16. DNA and Chromosomes  DNA Length  DNA is very long  DNA is coiled up into a very small space because it is in chromatin form  Chromosome Structure  Tightly packed chromatin is wrapped around small proteins called histones  When chromatin gets super coiled you create a chromosome

17. DNA Replication  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

18. Duplicating DNA  Before mitosis occurs, DNA needs to be duplicated first during interphase  When DNA duplicates, its called replication  DNA molecules separates into two strands, then produces two new complementary strands following the rules of base pairing  Each strand serves as a template for the new strand

19. How Replication Occurs  Enzymes help make new strands of DNA  One enzyme called helicase “unzips” the DNA, separating the base pairs  DNA polymerase 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. RNA & Protein Synthesis Sections 3-4

21. Structure of RNA  Made of nuleotides  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

22. Types of RNA  Three types of RNA  mRNA  Messenger RNA  rRNA  Ribosomal RNA  tRNA  Transfer RNA

23. Types of RNA  Messenger RNA  This is a copy of complimentary strand of DNA  Eventually will code for a protein to be made

24. Types of RNA  Ribosomal RNA  RNA found in ribosomes (organelles in the cell)  Ribosomes are the factory for protein synthesis

25. Types of RNA  Transfer RNA  Help produce a protein from mRNA  Brings amino acids (monomer of protein) to ribosome to bond them together and make a whole protein

26. Transcription  Taking DNA and making an RNA copy  Occurs in the cell’s nucleus  RNA polymerase opens the DNA and adds RNA copy to the template  Once this is made it is called pre-mRNA

27. RNA Editing  Pre-mRNA is a rough draft to the final copy of mRNA  Some parts of pre-mRNA are not needed to make a protein  These unnecessary parts are called introns  Introns get cut out of pre-mRNA  Before leaving the nucleus, mRNA needs to get a cap and tail to finalize the RNA strand

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

29. The Genetic Code  Each three letter codon represents an amino acid  DNA = AGCGTGCCA  RNA =  Codons =  Amino acids =

31. The Genetic Code  RNA knows when to start and stop based on the codons read  There is ONE start codon: AUG  There are THREE stop codons: UAA, UAG, UGA

32. Translation  Taking mRNA and making a protein  Occurs in the cytoplasm on a ribosome  tRNA brings specific amino acids to ribosome  If mRNA = AUG, then tRNA = UAC  The tRNA has the anti-codon

33. Translation  As new tRNA brings amino acids to the ribosome, past ones break off leaving just amino acids bonded to each other  This continues until one of the three STOP codons is met  Finished amino acid strand goes through protein folding

34. Mutations  Changes in the DNA sequence that affect the cell  Two types of mutations  Gene mutation  Chromosomal mutation

35. Gene Mutation  Point mutation  A change in one nucleotide in a DNA sequence  Occur only in a single point of the DNA  Can sometimes be a problem  Frameshift mutation  A change in the reading frame of DNA  Since DNA is read in 3 letter codons, if there is an insertion, deletion, or large change in these codons the frame is changed

36. Chromosomal Mutation  A change in the number of chrom0somes in the cell  Four types  Duplication  Deletion  Inversion  Translocation