Unit Thinking Questions • How big is DNA? • Does DNA have to stay in the nucleus? • If DNA controls the cell, how does it do so? • Does DNA communicate in its own language? • What happens if DNA is damaged? • Can DNA be used over again?
Objectives • I understand the structure and function of DNA • I can name the scientists involved in the discovery of DNA and explain the findings of their experiments • I can describe the structure and function of the 3 types of RNA
Homework • DNA Structure WS • Read chapter 12-1&12-2
How many chromosomes are in a typical human body cell? • 22 • 23 • 44 • 46 10
What type of organic compound is a DNA molecule? • Carbohydrate • Lipid • Protein • Nucleic Acid 10
Where is DNA found in a eukaryotic cell? • Nucleus • Nucleolus • Vacuole • Cytoplasm 10
What is the smallest unit (monomer) of a DNA molecule? • Amino acid • Monosaccharide • Nucleotide • Fatty acids 10
What nitrogen bases are found in DNA? • A,U,C,G • A,T,C,G • A,U,T,G • A,U,T,C 0% 0% 0% 0% 10
Which base bonds with Adenine (A)? • Guanine (G) • Cytosine (C) • Thymine (T) • Uracil (U) 10
What does DNA code for • Carbohydrates • Proteins • Lipids • Nucleic Acids 10
Quick Review – Cell Division • When do cells need to divide? • What is this type of cell division called? • How do the daughter cells compare to the parent cell? • How many daughter cells do we make from 1 parent cell?
MITOSIS 2N 2N 2N ALL CELLS AND DNA IDENTICAL
Mitosis • What are the phases of the cell cycle • Interphase • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis • Which of these steps are a part of mitosis? • What happens in interphase?
Phases of cell cycle • What are the stages of the cell cycle? • G1 • S • G2 • Mitosis/Cytokinesis • Which of these are part of interphase?
Sketch of the Cell Cycle Cells prepare for Division Cell Divides into Identical cells Daughter Cells DNA Copied Cells Mature
Which of the following is not a stage of interphase? • G1 • S • G2 • Mitosis 10
What important process occurs during S phase? • Cell growth • Preparation for division • DNA replication • Cyclins are generated 10
Which event occurs during interphase? • The cell grows. • Spindle fibers begin to form. • Centrioles appear. • Centromeres divide. 10
If a cell with 8 chromosomes divides by mitosis, how many chromosomes will be in each resulting daughter cell? • 2 • 4 • 8 • 16 10
History of DNA • Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA • Proteins were composed of 20 different amino acids in long polypeptide chains
Transformation • Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria • He found that R strain could become virulent when it took in DNA from heat-killed S strain • Study suggested that DNA was probably the genetic material • Experiment • Injected pathogenic and non-pathogenic bacteria into mice
Findings of Griffith’s Experiments • DNA can be transferred from dead to living bacteria (TRANSFORMATION)
Hershey and Chase • http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter14/hershey_and_chase_experiment.html
History of DNA • Chromosomes are made of both DNA and protein • Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material Radioactive 32P was injected into bacteria!
Hershey & Chase • Experiments • Radioactively labeled DNA and protein inside bacteriophages • Findings • Bacteria cells were being injected with the DNA of the viruses
Discovery of DNA Structure • Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G) • Experiment: • Found these amounts in a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.9%
C T A G Chargaff’s Rule • Findings • Adenine must pair with Thymine • Guaninemust pair with Cytosine • The bases form weak hydrogen bonds
Rosalind Franklin • Experiment • Took diffraction x-ray photographs of DNA crystals • Findings • DNA had a uniform diameter • DNA was a tightly wound helix
Watson and Crick • In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays • Experiment • Built 1st 3-D model of DNA • Findings for DNA • 2 strands • Antiparallel strands – run in opposite directions • Strands held together by Hydrogen bonds • Twisted ladder structure • First 3-D model
Griffith’s experiments showed that • dead bacteria could be brought back to life. • harmful bacteria were hardier than harmless bacteria. • heat caused the harmful and harmless varieties of bacteria to fuse. • genetic material could be transferred between dead bacteria and living bacteria. 10
The scientists credited with establishing the structure of DNA are • Avery and Chargaff. • Watson and Crick. • Mendel and Griffith. • Hershey and Chase. 10
Chargaff’s rules, or the base-pairing rules, state that in DNA • the amount of adenine equals the amount of thymine. • the amount of guanine equals the amount of cytosine. • the amount of guanine equals the amount of thymine. • Both a and b 10
DeoxyriboNucleicAcid • It is a nucleic acid • Monomer = Nucleotide • Deoxyribose sugar • Phosphate • Nitrogenous base • Contains C,H,O,N,P • Found in the nucleus of eukaryotes • Functions: 1. Heredity 2. Protein Synthesis 3. All Cell Activities
I.DeoxyriboNucleic Acid A. Made of nucleotides 1. Deoxyribose sugar 2. Phosphate 3. Nitrogen Base PHOSPHATE P G* D.S. NITROGEN BASE DEOXYRIBOSE SUGAR (5C) * A, T, or C
B. Shape of DNA is a Double Helix 1. Sides – alternating sugars and phosphates 2. Rungs – nitrogen bases D P D D P D A-T G-C P D P P D P C-G D P D T-A D P D G-C
Step One • Create a nucleotide using the model pieces