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

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

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 1962 - Watson and Crick won Nobel Prize (Franklin had already died)

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

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)

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

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

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

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

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

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