1. Chapter 11.1-11.3 – DNA STRUCTURE and FUNCTION
Mr. Martino
College Prep Biology

2. 11.1 Genes are made of DNA
1928, Frederick Griffith discovered the genetic role of DNA
Identified a “transforming factor”

3. 11.2 Nucleic acids store Deoxyribonucleic Acid (DNA): genetic material
Discovered by Johann Miescher
1953 James Watson and Francis Crick identified the structure of DNA as a double helix
Rosalind Franklin’s x-ray crystallography pictures were key
Watson and Crick won Nobel Prize (Franklin had already died)

5. 1952, Alfred Hershey & Martha Chase demonstrate DNA is genetic material of T2
Bacteriophages:
bacterial attacking viruses
Consist of DNA with protein coating

6. 11.2 DNA Structure DNA & RNA are nucleic acids Polymers of nucleotides
Nucleotides contain either ribose or deoxyribose sugar, P-group and one of 5 different kinds of N-bases:
Adenine
Thymine (DNA only)
Cytosine
Guanine
Uracil (RNA only)

7. Chargaff’s Rule: amount of A = T and the amount of C = G
DNA is a double helix
Sugar and P’s are the backbone
Nitrogenous bases pair to form rungs
N-bases are joined by H-bonds
Amounts of each base varies from species to species

8. 11.2 Con’t
Nucleotides (building blocks of DNA) are classified according to rings
Purines: double ringed – adenine and guanine
Pyrimidines: single ringed – thymine, cytosine and uracil
DNA is double stranded and RNA is single stranded

9. 11.2 Rosalind Franklin
Rosalind Franklin and Maurice Wilkins used X Ray crystallography to view DNA
Wilkins showed Watson her diffraction image of DNA
10 years after Franklin’s death, Watson acknowledged how her images helped in his discovery

10. 11.3 DNA Replication and Repair
DNA Replication: process of copying DNA before cell division
DNA must untwist, copy its two strands simultaneously
Rule = A-T and G-C
Enzymes unzip DNA
New nucleotides are bonded with old by DNA polymerases
DNA ligases fill in gaps
Enzymes wind DNA up to form helix
- Semiconservative: one side is old while other is new

13. DNA polymerases, ligases (glues), and other enzymes also engage in repair
DNA polymerase “proofreads”

14. Dolly, Daisies, and DNA
1997 – the first animal was cloned – Dolly a lamb
1. Remove nucleus from cell
2. Transfer nuclei from desired cells into unfertilized eggs
3. Implant the “zygote” into surrogate mother
Since Dolly – we have cloned mice, rats, cows, cats, mules, horses, and Rhesus monkeys along with a couple of endangered animals