2.  Deoxyribo- nucleic Acid is made up of nucleotides

3.  Nucleotides have 3 parts › Deoxyribose (sugar) › Phosphate group › Nitrogenous base

4.  Deoxyribose and Phosphate are in all nucleotides, but there are 4 different nitrogenous bases › Adenine › Guanine › Cytosine › Thymine

5.  All nitrogenous bases contain rings  Adenine and Guanine contain 2 rings and are called Purines  Cytosine and Thymine contain 1 ring and are called Pyrimidines  Remember the phrase: › Pure As Gold

6.  In 1953, Scientists Watson and Crick made a model of DNA as a double helix – the spiral staircase shape.  When untwisted looks like a ladder  The sides of the ladder are the backbone and alternate with deoxyribose and phosphate

7.  The bases bond the two strands in the middle  A purine always bonds with a pyrimidine so the length is the same  They are bonded together by hydrogen bonds

8.  Cytosine always bonds with Guanine › Hint: (C and G are letters that look alike)  Adenine always bonds with Thyamine › Hint: (A and T are letters made of straight lines)

10.  The order and sequence of these bases is what makes each of us different from one another and different from other species