 Levene, 1920s  Nucleotides make up DNA  Nucleotides have three parts:  Sugar  Phosphate  Nitrogen Base

 Griffith, 1928  Transformation of some information from dead S bacteria to live R bacteria  What is the transforming substance? Avery, 1944 Isolate macromolecules (DNA, protein, carbohydrates, lipids) to figure out what was transformed in Griffith’s experiment.

 Chargaff, 1950  Amount of Guanine = Amount of Cytosine  Amount of Adenine = Amount of Thymine

 Franklin, 1951  Used X-ray diffraction to take a picture of a DNA molecule

 Hershey and Chase, 1952  Tracked viral DNA in a bacteria  Saw that DNA, not protein, was inherited

 Watson and Crick, 1953  Used Franklin’s photo to finalize DNA structure  Double Helix or twisted ladder

phosphate deoxyribose Nitrogen base NUCLEOTIDE COMPLEMENTARY BASE PAIR

 Phosphate groups covalently bond to deoxyribose  Covalent bonds are STRONG bonds in which electrons are SHARED!  Phosphate and sugar make DNA “backbone”  FOUR different nitrogen bases  Two are PURINES-two ringed ▪ Adenine (A), guanine (G)  Two are PYRIMIDINES-single ringed ▪ Thymine (T), cytosine (C)

 The order of the nitrogen bases in a gene determines what proteins are made  Each gene segment codes for specific amino acids  The proteins that are made determines the phenotype for the trait

 The specific order and type of base is important!  THE CAT ATE THE BAT  THE CAT ATE THE TAB  THE CAT ATE THE RAT ▪ Huge difference between a bat, tab, and rat!!

 DNA is composed of TWO strands which are linked and twist to form a double helix; looks like a “twisted ladder”  Nucleotides of both strands join following base pairing rules  Strands are held together by weak hydrogen bonds connecting the nitrogen bases

 Purines and pyrimidines are complementary  One strand of DNA determines the other according to its bases  Adenine ALWAYS pairs with thymine  A T  Guanine ALWAYS pairs with cytosine  G C

 In order for a cell to pass on its genetic information, DNA must be replicated before cell division so new cells can have the same DNA  DNA replication involves: 1. Unwinding the double helix 2. Separating the two strands of DNA to create templates (DNA helicase) 3. Adding free nucleotides to both strands to create new complements (DNA polymerase) ▪ Each double stranded DNA molecule now has one old strand and one new strand

 HELICASE unwinds and unzips the original strand  PRIMASE adds a short RNA primer to start replication on the leading strand  DNA POLYMERASE adds DNA nucleotides to the leading strand from 5’ to 3’ continuously (toward Helicase)  PRIMASE adds a short RNA primer to start replication on the lagging strand  DNA POLYMERASE adds DNA nucleotides to the lagging strand from 5’ to 3’ discontinuously (away from Helicase) making Okazaki Fragments  DNA POLYMERASE 1 changes the RNA primer to DNA nucleotides  LIGASE glues the Okazaki fragments together.

 Enzymes play an important role in DNA replication  DNA helicase-unwinds DNA for replication  DNA polymerase-adds free nucleotides; also proofreads the new DNA strand for any mistakes to prevent mutations

 All of an organism’s somatic cells have the SAME DNA;  nitrogen bases are in the SAME order and code for the SAME proteins

Swap your 2 nd and 3 rd picture segments Delete the 3 rd picture segment

Insert the 4 th picture segment after the 1 st picture segment Duplicate the 1 st picture segment

 Point mutations (changes at one point)  Substitution ▪ Switch nitrogen bases (so instead of A you get G)  Frameshift mutations (moves the DNA sequence)  Insertion  Deletion  Duplication  Tandem Repeats

 Missense  DNA sequence now codes for a different amino acid  Nonsense  DNA sequence codes for STOP too early

 Mutagens  Examples?

 Clone: an organism that has the same exact DNA as another organism  Natural (think asexual reproduction) or lab- made  Each clone starts out as an egg then grows into an adult, just like all organisms

 Inserting DNA from one organism into the DNA of another organism  Transgenic organisms  Animals – lab settings  Plants – agriculture  Recombinant DNA  Genetically Modified Organisms

 Study individual genes  Treat some diseases  Generate insulin for diabetic medicine  Factor VIII (blood clotting for hemophiliacs)  Insert new genes into organisms

 Altering the expression of a gene to treat a disease or disorder  Treatment v. Enhancement

 Identify non-protein coding regions that are unique to individuals  Uses gel electrophoresis to separate the DNA fragments  Who did it?