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Biology Chapter 12 Section 1 DNA
Transcript of Biology Chapter 12 Section 1 DNA
thymine (T) The Components and Structure of DNA Alfred Hershey and Martha Chase studied viruses—nonliving particles smaller than a cell that can infect living organisms. The Hershey-Chase Experiment Copyright Pearson Prentice Hall Transformation
Griffith called this process transformation because one strain of bacteria (the harmless strain) had changed permanently into another (the disease-causing strain).
Griffith hypothesized that a factor must contain information that could change harmless bacteria into disease-causing ones. Griffith and Transformation Griffith set up four individual experiments.
Experiment 1: Mice were injected with the disease-causing strain of bacteria. The mice developed pneumonia and died. Griffith and Transformation Griffith made two observations:
(1) The disease-causing strain of bacteria grew into smooth colonies on culture plates.
(2) The harmless strain grew into colonies with rough edges. Griffith and Transformation In DNA, the following base pairs occur:
A with C, and G with T.
A with T, and C with G.
A with G, and C with T.
A with T, and C with T. Chargaff's rules state that the number of guanine nucleotides must equal the number of
thymine plus adenine nucleotides. DNA is a long molecule made of monomers called
sugars. The Hershey-Chase experiment was based on the fact that
DNA has both sulfur and phosphorus in its structure.
protein has both sulfur and phosphorus in its structure.
both DNA and protein have no phosphorus or sulfur in their structure.
DNA has only phosphorus, while protein has only sulfur in its structure. Avery and other scientists discovered that
DNA is found in a protein coat.
DNA stores and transmits genetic information from one generation to the next.
transformation does not affect bacteria.
proteins transmit genetic information from one generation to the next. Using clues from Franklin’s pattern, James Watson and Francis Crick built a model that explained how DNA carried information and could be copied.
Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other. The Double Helix Rosalind Franklin used X-ray diffraction to get information about the structure of DNA. We still didn't know what the shape of
the DNA molecule was. DNA is a polymer made up of the monomer nucleotides.
A nucleotide is made up of:
Deoxyribose – 5-carbon Sugar
Nitrogenous Base The Components and Structure of DNA If P-32 was found in the bacteria, then it was the DNA that had been injected. The Hershey-Chase Experiment Bacteriophages
A virus that infects bacteria is known as a bacteriophage.
Bacteriophages are composed of a DNA or RNA core and a protein coat. The Hershey-Chase Experiment Griffith concluded that the heat-killed bacteria passed their disease-causing ability to the harmless strain. Griffith and Transformation Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died. Griffith and Transformation Experiment 3: Griffith heated the disease-causing bacteria.
He then injected the heated bacteria into the mice.
The mice survived. Griffith and Transformation Experiment 2: Mice were injected with the harmless strain of bacteria. These mice didn’t get sick. Griffith and Transformation In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused pneumonia.
He isolated two different strains of pneumonia bacteria from mice and grew them in his lab. Griffith and Transformation 12–1 DNA This principle is called base pairing addresses the hydrogen bonding between only certain nitrogenous bases.
Base Pair Rules The Components and Structure of DNA Erwin Chargaff discovered that:
The number of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA.
The number of adenine [A] and thymine [T] bases are almost equal in any sample of DNA. The Components and Structure of DNA If S-35 was found in the bacteria, it would mean that the viruses’ protein had been injected into the bacteria. The Hershey-Chase Experiment Why am
I here? Why was this necessary? Can you explain why
he did this? Why? I'm
Ever! How did this happen? What was that factor? Sulfur is used in protein and not DNA. Phosphorus is used in DNA and not Protein. This led to the base pair rules. Are hyrdogen
bonds strong or weak?