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AP Biology ch. 16.1
HISTORY OF DNA
1869, Friedrich Miescher discovers nuclein by extracting white blood cells from pus-laden bandages
DNA HISTORY: MIESCHER
1928: tried to find a pneumonia vaccineFound “transforming principle” instead
DNA HISTORY: FREDERICK GRIFFITH
1944: Followed up on Griffi th’s experimentDemonstrated that DNA was Griffi th’s “transforming
principle”
DNA HISTORY: AVERY & MCCARTY
1952: Used phages to demonstrate that DNA was genetic material
Radiolabeled phages with 35S and 32P to distinguish protein from nucleic acid
DNA HISTORY: HERSHEY & CHASE
1950: determined that adenine molecules always pair with Thymine molecules and cytosine molecules always pair with guanine molecules
DNA HISTORY: ERWIN CHARGAFF
1953: Used X-ray diff ractionHad the evidence that the double helix existed but
didn’t put it all together
DNA HISTORY: FRANKLIN & WILKINS
1953: Saw Franklin’s X-rays, and built the fi rst, correct, 3D model of DNA
DNA HISTORY: WATSON & CRICK
Many scientists expanded upon previous scientific ideas to correctly show: Structure of DNA (double helix of nucleotides) Function of DNA (genetic material of life)
SUMMARY OF DNA HISTORY
Chromosomes: DNA wound up around histone proteins
Onion (8 pairs) Human (23 pairs)
OVERVIEW: DNA STRUCTURE
Long molecule made up of repeating units called nucleotides
OVERVIEW: DNA STRUCTURE
Nucleotide: 5-Carbon Sugar (Deoxyribose) Phosphate Group (PO4) Nitrogen Base:
Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
OVERVIEW: DNA STRUCTURE
Important Chemistry of DNA: Nitrogen base groups:
Purines (2 ring) Adenine Guanine
Pyrimidines (1 ring) Cytosine Thymine
OVERVIEW: DNA STRUCTURE
Important Chemistry of DNA: Sugar carbon atoms are numbered (1-5) Phosphodiester bonds hold backbone together Hydrogen bonds hold nitrogen bases together
OVERVIEW: DNA STRUCTURE
AP Biology ch 16.2
DNA REPLICATION
You started as: one cell with one set of DNA
Now you are: trillions of cells large Each cell contains the one set of DNA
REMEMBER
DNA Replication Process by which DNA is copied Occurs in all living organisms Many enzymes are used!
HOW DOES EACH CELL GET DNA?
DNA STRUCTURE
Start with one complete strand of DNA Template Strand Parent Strand
STEP 1: DNA REPLICATION
Topoisomerase unwinds DNA
STEP 2: DNA REPLICATION
Helicase Unzips template strand At H bonds
STEP 3: DNA REPLICATION
Replication fork forms
STEP 4: DNA REPLICATION
DNA polymerase Finds starter sequence Adds free DNA nucleotides Checks the sequence Makes repairs
STEP 5: DNA REPLICATION
DNA is antiparallelOne strand of DNA:
synthesized continuouslyThe other strand of DNA:
is synthesized in segments (O.F.)
STEP 6: OKAZAKI FRAGMENTS
DNA Ligase Connects O.F.
STEP 7: DNA REPLICATION
Two identical strands of DNA are formedEach strand has a parent and daughter strand
STEP 8: DNA REPLICATION
THE OTHERS
PBS: http://www.youtube.com/watch?v=5VefaI0LrgE
St. Olaf: http://
www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf
REPLICATION ANIMATIONS
GENE EXPRESSION
