DNA History, Structure, & Function AP Biology

History of DNA AP Biology ch. 16.1

DNA History: Miescher 1869, Friedrich Miescher discovers nuclein by extracting white blood cells from pus-laden bandages

DNA History: Frederick Griffith 1928: tried to find a pneumonia vaccine Found “transforming principle” instead

DNA History: Avery & McCarty 1944: Followed up on Griffith’s experiment Demonstrated that DNA was Griffith’s “transforming principle”

DNA History: Hershey & Chase 1952: Used phages to demonstrate that DNA was genetic material Radiolabeled phages with 35S and 32P to distinguish protein from nucleic acid

DNA History: Erwin Chargaff 1950: determined that adenine molecules always pair with Thymine molecules and cytosine molecules always pair with guanine molecules

DNA History: Franklin & Wilkins 1953: Used X-ray diffraction Had the evidence that the double helix existed but didn’t put it all together

DNA History: Watson & Crick 1953: Saw Franklin’s X-rays, and built the first, correct, 3D model of DNA

Summary of DNA History Many scientists expanded upon previous scientific ideas to correctly show: Structure of DNA (double helix of nucleotides) Function of DNA (genetic material of life)

Overview: DNA Structure 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

DNA Replication AP Biology ch 16.2

Remember You started as: Now you are: one cell with one set of DNA trillions of cells large Each cell contains the one set of DNA

How does each cell get DNA? DNA Replication Process by which DNA is copied Occurs in all living organisms Many enzymes are used!

DNA Structure

Step 1: DNA Replication Start with one complete strand of DNA Template Strand Parent Strand

Step 2: DNA Replication Topoisomerase unwinds DNA

Step 3: DNA Replication Helicase Unzips template strand At H bonds

Step 4: DNA Replication Replication fork forms

Step 5: DNA Replication DNA polymerase Finds starter sequence Adds free DNA nucleotides Checks the sequence Makes repairs

Step 6: Okazaki Fragments DNA is antiparallel One strand of DNA: synthesized continuously The other strand of DNA: is synthesized in segments (O.F.)

Step 7: DNA Replication DNA Ligase Connects O.F.

Step 8: DNA Replication Two identical strands of DNA are formed Each strand has a parent and daughter strand

The Others

Replication Animations PBS: http://www.youtube.com/watch?v=5VefaI0LrgE St. Olaf: http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf

Gene Expression

DNA Function (Gene Expression)