Target #1- I can describe the experiment conducted by Frederick Griffith
• Frederick Griffith
– A British medical officer
– Studied a bacterium called Streptococcus pneumoniae
• Can cause pneumonia in mammals
– He was trying to develop a vaccine against the virulent strain, disease causing strain, of the bacterium

Target #1- cont.
• Each virulent bacterium is surrounded by a capsule made of polysaccharides that protects it from the body’s defense system
– S strain: a virulent strain of bacteria that grows into smooth-edged colonies
– R strain: a non-virulent strain of bacteria that grows into rough colonies

• Griffith used the two strains of bacteria in a series of 4 experiments
– Provide insight about the nature of the hereditary material.
Target #1- cont.

• Griffith concluded that heat-killed virulent bacterial cells release a hereditary factor that transfers the diseasecausing ability to the live harmless cells
– Transformation: the transfer of genetic material from one cell to another cell or from one organism to another organism
Target #2- I can explain
Griffiths conclusions

• Oswald Avery
– An American researcher who wanted to test whether the transforming agent in Griffith’s experiment was protein, RNA, or DNA
– Used enzymes to separately destroy each of the three molecules in heat-killed S cells
• Protease enzyme  killed the protein in the S cells
• Dnase enzyme  killed the DNA in the S cells
• Rnase enzyme  killed the RNA in the S cells
– Injected mice with each of the three types of heat-killed S cell batches with live R cells

Target #4- I can explain the conclusions of the Avery experiment
–Conclusions
• The cells missing protein and RNA were able to transform R cells into S cells and kill the mice
• Cells missing DNA did not transform R cells into S cells
–Mice survived
• Concluded that DNA is responsible for transformation in bacteria

Target #5- I can describe the
Hersey-Chase
Experiment
• Hershey-Chase
Experiment
– Martha Chase & Alfred
Hershey
– Set out to test whether DNA or protein was the hereditary material viruses transfer when viruses enter a bacterium
• Viruses that infect a bacterium are known as bacteriophages

• Step 1: radioactive isotopes were used to label the protein and DNA in the bacteriophages
– Sulfur: protein label
– Phosphorus: DNA label
• Step 2: Allowed protein-labeled and DNA-labeled bacteriophages to infect E. Coli bacteria
• Step 3: removed the bacteriophage coats from the cells in a blender
• Step 4: used a centrifuge to separate the bacteriophage from the E. Coli
• Conclusions: found that all of the viral DNA and little of the protein had entered E. Coli cells
– DNA is the hereditary molecule in viruses
Target #6- I can state the steps of the Hershey-
Chase experiment

Target #7- I can identify the full name for DNA
Target #8- I can state what DNA is made of
• DNA stands for deoxyribonucleic acid
• The DNA molecule is a long polymer, or chain, of repeating units
– The monomers of DNA are called nucleotides
– Each nucleotide has 3 parts
• Phosphate group
• Deoxyribose sugar
• Nitrogen base

• One molecule of human
DNA contains billions of nucleotides
– 4 types of nucleotides, known as nitrogen bases
• Cytosine (C)
• Thymine (T)
• Adenine (A)
• Guanine (G)
– The order of nitrogen bases on a chain of DNA is called a base sequence

• Purines: a group of nitrogen bases that includes adenine and guanine
• Pyrimidines: a group of nitrogen bases that includes thymine and cytosine

Target #11- I can explain what Chargaff discovered about DNA
• Erwin Chargaff
– Found that the same four bases are found in the DNA of all organisms
– The proportion of the four bases differs from organism to organism
– Chargaff’s Rule
• Adenine bonds to
Thymine
– A  T
• Cytosine bonds to
Guanine
– C  G

Target #12- I can explain what Rosalind
Franklin discovered about DNA
• Rosalind Franklin
– Studied DNA using x-ray crystallography
• The DNA, when bombarded with x-rays, an image can be captured from the refracted light
– X-ray photographs showed an X surrounded by a circle
• Used later by James Watson & Francis Crick to further develop the shape of DNA

• James Watson & Francis
Crick
– One of the many scientists to study proteins and the structure of DNA
– Built a model of DNA using wood and metal
• Found that DNA fits together like a puzzle
• The base pair combinations discovered by Chargaff were confirmed to be accurate
– Double Helix: two strands of DNA wind around each other like a twisted ladder
Target #13- I can explain what Watson
& Crick discovered about DNA

• The DNA nucleotides of a single strand are joined together by covalent bonds
– Connect the sugar of one nucleotide to the phosphate of the next nucleotide
– The two strands of the helix are held together by hydrogen bonds
• Chargaff’s rules are more commonly known as base pairing rules
– T always pairs with A
– C always pairs with G