2.  This very large molecule called Deoxyribonucleic acid contains information.  DNA information codes for proteins that make up muscle, enzymes, & the structures of organisms.  A gene is a section of DNA coding for a protein.

3.  DNA has a uniform diameter (Franklin)  DNA is a double helix (Watson and Crick)  Adenine pairs with Thymine & Guanine pairs with Cytosine (Chargaff)  The two strands are built in opposite directions.

4.  Backbone or rails of the ladder: alternating deoxyribose and phosphate.  Deoxyribose: a sugar  Phosphate: a negative ion containing phosphorus  Alternating pattern

5.  Nitrogenous bases contain nitrogen  Pairs: › A-T › G-C  Pyrimidines: 1 ring › Thymine › Cytosine  Purines: 2 rings › Adenine › Guanine

6.  Hydrogen bonds connect A-T or G-C pairs.  H bonds are weak forces between partial positive and negative charges on atoms— works like magnets.

7.  Patterns of Inheritance--1857  Gregor Mendel studied peas the and passage of traits from one generation to another. › What could carry the information from one individual to another?

8.  Experiment: mice and 2 types of pneumonia (virulent and non-virulent).  Proved chemical transfer of information.

9.  Chargaff studied the DNA of different species from different kingdoms and different phyla.  The amount of Adenine was close to equal to the amount of Thymine.  The amount of Guanine was close to the amount of Cytosine.  Chargaff’s Rule  http://www.dnalc.org/resources/3d/21-chargaff-ratios.html http://www.dnalc.org/resources/3d/21-chargaff-ratios.html

10.  Studied the structure of DNA using a technique called X- ray diffraction.  The repeating ‘x’ patterns imply a twisting coiled shape: helix.  The molecule has uniform diameter and uniform repeat to the twist.

11.  They worked to develop three dimensional model of DNA that would explain properties of the molecule.  Franklin’s work gave them a vital clue.  The molecule was a double helix with the bases making the rungs of a ladder.  One page paper was published April 1953

12.  To pass information to another organism, the data which is stored in the DNA must be copied.  Process is called DNA Replication  A replica is an exact copy  How does DNA replicate?  How does its structure work to make copies?

13.  Both strands carry the same information.  1) Unwind the helix.  2) Unzip the strands to make two templates to use in making copies.  3) Build a complementary strand one nucleotide at a time for two identical molecules. Replication Fork

14.  Follow Chargaff’s Rule: A=T and G=C  Find the bases that complement this strand: A T T T GCG TAACCGA TAAA CGCAT T GGCT

15.  Which model would work?

16.  Enzyme that unwinds the double helix.  Name comes from the helix shape of DNA that the enzyme straightens out. Helicase

17.  This protein enzyme that connects the nucleotides together to make the polymer.  It proofreads the sequences.  Most accurate enzyme Polymerase DNA Polymerase

18.  DNA is an enormously long molecule.  How do you pack and move DNA?  http://www.dnalc.org/resources/3d/07- how-dna-is-packaged-basic.html http://www.dnalc.org/resources/3d/07- how-dna-is-packaged-basic.html

19.  Wind DNA around histone core like a spool of thread.  Nucleosome  Wind coiled DNA into second supercoil.  Condensed chromosome

20.  http://www.dnai.org/timeline/ http://www.dnai.org/timeline/