Chapter 12.1 DNA: Molecule of Heredity

I. DNA: Molecule of Heredity A. Properties of DNA 1. Makes up chromosomes 2. Controls cell activity and an organism’s traits by determining the structure of proteins. 3. Polymer of nucleotides.

B. Structure of nucleotides 1. 5- Carbon sugar (deoxyribose or ribose) 2. Phosphate group 3. Nitrogenous base Nitrogenous base Phosphate group Sugar (deoxyribose)

C. DNA has four possible nitrogen bases: 1. Adenine (A) 2. Guanine (G) 3 Cytosine (C) 4. Thymine (T) 5. Types of Bases: a. Purine: A & G b. Pyrimidine: C & T

6. Chargaff’s Experiments Bonding of Pairs: C bonds with G A bonds with T 7. So the amount of Adenine = the amount of thymine and the amount of cytosine = the amount of guanine.

D. Structure of DNA 1. Double Helix structure confirmed in 1953 by Watson and Crick 2. Watson and Crick won Nobel Prize for the model of DNA. 3. However their discovery was based on Rosalind Franklin’s X-ray diffraction techniques and Chargaff’s bonding rules. 3. Determined that the double helix structure is twisted. Watson and Crick with their model

E. Importance of Nucleotide Sequences 1. The sequence of nucleotides forms the unique genetic information of an organism. 2. The closer the relationship is between two organisms, the more similar their DNA nucleotide sequences will be Click in box to play movie

12.2 I. Replication of DNA A. Before a cell can divide by mitosis or meiosis, it must make a copy of the chromosomes – REPLICATION. * If this did not happen, a new cell would have only half the amount of DNA of its parent.

B. Enzymes break hydrogen bonds between N bases. C Strands unzip and free nucleotides bond to open bases on the strands = Base Pairing D. When all DNA is duplicated, mitosis or meiosis can take place.

DNA Nucleotide : Use to aid with diagram