Chapter 10

Do Now: Read ) Define bacteriophages 2) Why are viruses on the fence between life and nonlife? 3) What are we going to explore in this chapter?

10.1 Experiments that showed that DNA is the genetic material 1928: Griffith – Two strains of a bacteria (one strain caused pneumonia and the other strain was harmless) – Exp: heat killed harmful bacteria mixed with living harmless bacteria – Result: living harmful bacteria What can we conclude from this experiment?

1940: Scientists knew that eukaryotic chromosomes were made of protein and DNA Why did most scientists think that protein was the genetic material? – Proteins are made up of 20 different amino acids Can have complex structure and functions – DNA is simple Four nucleotides

1952: Alfred Hershey& Chase pg 185 T2 virus is made of DNA and protein Batch 1) Grew virus in radioactive* sulfur (proteins contain sulfur and DNA does not) Batch 2) Grew virus in radioactive* phosphorus (phosphate w/oxygen) Steps: – 1) Allowed batches to attack bacteria – 2) Shook off any outside viral parts – 3) Spun with centrifuge, cells to the bottom – 4) Measured radioactivity in liquid vs. pellet Result: Batch 1: protein* on the outside Batch 2: DNA* in cell Conclusion:

10.2: DNA and RNA Description – What is DNA? A biological code to make proteins that can be passed from one generation to the next Deoxyribonucleic Acid DNA is made up of nucleotides (sugar (deoxyribose, phosphate and a nitrogenous base) Polynucleotide is many nucleotides join to form a long chain of DNA RNA uses ribose as sugar, uracil in place of thymine, and is single stranded

10.3DNA 3D model discovered by Watson/ Crick and Rosalind Franklin What does DNA look like? A double helix- similar to a twisted ladder The sides are made up of the sugar and phosphates (backbone) The rungs of the ladder are made up of the nitrogenous bases held together by hydrogen bonds The four bases are Adenine (A), Guanine (G), Thymine(T) and Cytosine (C) – Complementary base pairing Pyrimidine- purine – Adenine bonds to thymine (T-A) – Guanine bonds to Cytosine (G-C) DNA is wrapped around proteins called histones to create the condensed form called chromatin DNA is able to mutate slightly overtime to allow for variation and evolution

10.2 A-B Draw the following structures on page 186 and 187 Polynucleotide Sugar phosphate backbone DNA nucleotide Pyrimidines Purines HW: Exercise 1 in packet