1. DNA Deoxyribonucleic acid Helical shape/twisted ladder Found in the nucleus of every single cell of every single living or once living organism Is unique to each individual with the exception of identical twins Carries the code that gives us our traits and characteristics

2. DNA Structure The four nitrogenous bases that make up DNA are: 1.Adenine 2.Guanine 3.Cytosine 4.Thymine

3. DNA Structure Exterior backbone (uprights of ladder) –Sugar and phosphate arranged in an alternating pattern along the entire strand of DNA Interior (rungs of ladder) –Made up of 4 bases that pair in a certain way –Bases attached ONLY to sugars NOT phosphates A-T G-C

4. LE 16-5 Sugar–phosphate backbone 5 end Nitrogenous bases Thymine (T) Adenine (A) Cytosine (C) DNA nucleotide Phosphate 3 end Guanine (G) Sugar (deoxyribose)

5. DNA molecule is made up of two strands, forming a double helix there are two sugar-phosphate backbones, with the nitrogenous bases paired in the molecule’s interior C—G A—T

6. Watson and Crick noted that the specific base pairing suggested a possible copying mechanism for genetic material Since the two strands of DNA are complementary, each strand acts as a template for building a new strand in replication Watson and Crick’s semiconservative model of replication predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand

7. LE 16-9_4 The parent molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding with its specific partner, A with T and G with C. The first step in replication is separation of the two DNA strands. Each parental strand now serves as a template that determines the order of nucleotides along a new, complementary strand. The nucleotides are connected to form the sugar-phosphate back- bones of the new strands. Each “daughter” DNA molecule consists of one parental strand and one new strand. DNA basics tutorial rotating DNA crash course