Chapter 12 DNA & RNA

Interest Grabber Order! Order! Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message. Section On a sheet of paper, write the word cats. List the letters or units that make up the word cats. 2. Try rearranging the units to form other words. Remember that each new word can have only three units. Write each word on your paper, and then add a definition for each word. 3. Did any of the codes you formed have the same meaning? 4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message?

I.DNA A. Griffith & Transformation Frederick Griffith was trying to figure out how bacteria made people sick-how they cause a certain type of pneumonia. He isolated 2 strains(types) from mice-both cultured well,but only one caused pneumonia.The culture of the disease causing bacteria were __________________colonies while the other was rough. smooth

1-Griffith’s experiments (1928)  Mice injected w/ disease –causing strain got sick and died and nothing happened if injected w/other strain…He wondered if the disease-causing type made a toxin…?  So he took some of disease strain and heated to kill bacteria and then injected into mice….mice survived suggesting it was not a toxin producing disease

Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment

Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment

2-Transformation He mixed his heat –killed w/ live harmless bacteria and injected into mice…..________________________ Somehow the disease –causing strain passed their disease capacity to harmless bacteria….. disease – causing strain found in lungs He called this changing of one bacteria by the genes of another _____________________....Thus a factor(gene) from heat killed disease –causing strain was passed on. Mice developed pneumonia transformation

B. Avery & DNA Team of scientists lead by Avery in 1944 repeated Griffith’s experiment in order to determine which molecule was responsible for the transformation. They made an extract from the heat-killed bacteria and treated it w/enzymes that kill proteins,lipids and other molecules,inc. RNA

Avery cont’d ____________________still occurred so the above molecules were not responsible for transformation They repeated the experiment but used enzymes that kill____________, stopping transformation…. Therefore ________caused the transformation and thus stores and transmits genetic info transformation DNA

C. The Hershey –Chase Experiment 1952-Alfred Hershey and Martha Chase studied viruses-disease-causing particles smaller than a cell. ______________________-virus that infects bacteria.They have a DNA or RNA core and a protein coat…They attach to the surface of a bacterium and inject genetic info into cell.The viral genes act to produce many new bacteriophages and eventually destroy bacterial cell,w/_____________bursting out. bacteriophage viruses

They grew viruses in cultures containing _________________________________,mixed them w/bacteria and waited a few min. for viruses to inject genetic material. Then they separated the bacteria from the viruses and tested bacteria for radioactive marker…..nearly all the radioactivity was P-32-found in _________---- thus concluding it was the genetic material was DNA ! Radioactive markers DNA

Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1

Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Section 12-1 Figure 12–4 Hershey-Chase Experiment

Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Section 12-1 Figure 12–4 Hershey-Chase Experiment

D. The Components and Structure of DNA Scientists questioned how the DNA molecule could do three things 1)carry info from 1 generation to the next 2)putting that info to work and 3)could be easily copied DNA is a long molecule made of units called ___________________________________________- nucleotides

The nucleotide is made of 3 basic parts:______________________(sugar), a phosphate group and a_________________________________ deoxyribose Nitrogenous base

2 nitrogenous bases are purines(have 2 rings):___________________________(A)and_______ (G) 2 other nitrogenous bases are pyrimidines (have 1 ring):____________________(C)and ____________________________(T ) Adenine,guanine Cytosine and thymine -- backbone made by sugar and phosphate w/ bases sticking out sideways

PurinesPyrimidines AdenineGuanine CytosineThymine Phosphate group Deoxyribose Figure 12–5 DNA Nucleotides Section 12-1

1-_______________________Rules-discovered that %’s of Cytosine and guanine were almost equal in DNA and the same was true for adenine and thymine….Thus A pairs w/T and C w/ G-BASE PAIRING Chargaff’s Rules

Percentage of Bases in Four Organisms Section 12-1 Source of DNAATGC Streptococcus Yeast Herring Human Streptococcus Yeast Herring Human

2- X-ray evidence-1950’s –Rosalind Franklin used X-ray diffraction to learn about DNA structure----The scattered X pattern seen begins to show the __________-partial TWISTED STRUCTURE of DNA helix

 3---Double helix_ Watson and Crick -2 strands wound around each other---like the twisted ladder or spiral staircase Strands held together by H-bonds

Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Figure 12–7 Structure of DNA Section 12-1