DNA: The Genetic Material Chapter 14 1

Discovery of DNA Griffith Avery, MacLeod, McCarthy Hershey and Chase 2

Discovery of DNA’s Structure Chargaff’s Rule Franklin’s Helix Watson and Crick’s Double Helix 3

W & C’s DNA Structure 5´5´ 3´3´ P P P P OH 5-carbon sugar Nitrogenous base Phosphate group Phosphodiester bond O O O O 4´4´ 5´5´ 1´1´ 3´3´ 2´2´ 4´4´ 5´5´ 1´1´ 3´3´ 2´2´ 4´4´ 5´5´ 1´1´ 3´3´ 2´2´ 4´4´ 5´5´ 1´1´ 3´3´ 2´2´ Nitrogenous basesDouble helix 4

DNA Structure DNA is a nucleic acid Composed of repeating units called ‘nucleotides’. Each nucleotide is made up of: – 5-carbon sugar called a “deoxyribose sugar” – Phosphate group (PO 4 ) Attached to 5′ carbon of sugar – Nitrogenous base Adenine, thymine, cytosine, guanine – Free hydroxyl group (—OH) Attached at the 3′ carbon of sugar 5

DNA Strand 6

The DNA Double Helix 7

Replication Review ChromatinChromosome 8

9

DNA Replication Requires 3 things – Something to copy Parental DNA molecule – Something to do the copying Enzymes – Building blocks to make copy Nucleotide s 10

DNA Replication DNA replication includes – Initiation – replication begins – Elongation – new strands of DNA are synthesized by DNA polymerase – Termination – replication is completed 11

12

13

14

Prokaryote/Eukaryotic DNA Prokaryotes Eukaryotes Shape: Complexity: Size: Replication: Gene Expression: 15

Benefits of Chromosomes Increased genetic variation Improved genetic stability Increased complexity Allows organisms to be diploid 16

DNA Repair Errors occur due to: – replication mistakes – mutagens DNA repair is vital to the cell. 17

DNA Repair Falls into 2 general categories: 1.Specific repair – Targets a single kind of error in DNA and repairs only that damage 2.Nonspecific – Use a single mechanism to repair multiple kinds of errors in DNA 18

Photorepair Specific repair mechanism for one particular form of damage caused by UV light. 19

Excision repair Nonspecific repair Damaged region is removed and replaced by DNA synthesis 20