In 1928, Frederick Griffith, a bacteriologist, was trying to prepare a vaccine against pneumonia.

Slides:



Advertisements
Similar presentations
How to Use This Presentation
Advertisements

DNA: The Genetic Material
Ch. 9 Notes DNA: The Genetic Material
Chapter 9 DNA: THE Genetic Material
DNA and Replication.
Chapter 13 DNA, RNA and Proteins.
Chapter 9 DNA: THE Genetic Material. Transformation Frederick Griffith, a bacteriologist, prepared a vaccine against pneumonia Vaccine – a substance that.
DNA and Heredity. DNA and Heredity DNA is found in the cell’s __nucleus_______. DNA is found in the cell’s __nucleus_______. In the nucleus, we find the.
Nucleic Acids The Genetic Material. Two types of Nucleic acids RNA RNA DNA DNA.
1 2 History of DNA Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins were composed of.
DNA Structure. Frederick Griffith In 1928, Frederick Griffith wanted to learn how certain types of bacteria produce pneumonia Griffith injected mice with.
Chapter 12 DNA & RNA.
DNA: The Stuff of Life. Griffith and Transformation In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused.
DNA: The Genetic Material
Zoology. I. Discovery of DNA A. Objectives i. Relate how Griffith’s bacterial experiments showed that a hereditary factor was involved in transformation.
What is DNA? Where is it located?
I. Scientist 1.Frederick Griffith 2.Oswald Avery 3.Alfred Hershey 4.Martha Chase 5.Erwin Chargaff 6.Rosalind Franklin 7.Maurice Wilkins 8.James Watson.
Chapter 12: DNA & RNA. Section 12.1 – Structure of DNA DNA – Deoxyribonucleic Acid; traits are determined by your genes, genes code for proteins, and.
DNA: The Genetic Material
12–1 DNA Photo credit: Jacob Halaska/Index Stock Imagery, Inc.
DNA: The Stuff of Life. Griffith and Transformation In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused.
Chapter 11 DNA & GENES.
13.1: The Structure of DNA.
12.1 Identifying the Substance of Genes. Lesson Overview Lesson Overview Identifying the Substance of Genes THINK ABOUT IT How do genes work? To answer.
DNA The Molecular Basis of Inheritance BEA5-C588-4A4E-AB ED8BE7DB.
DNA.
DNA: The Genetic Material
Chapter 9 DNA: The Genetic Material
DNA, RNA, and Proteins Section 1 Section 1: The Structure of DNA Preview Bellringer Key Ideas DNA: The Genetic Material Searching for the Genetic Material.
Ch. 9 How Genes Work. Ch. 9-1 Understanding DNA How Scientists Identified the Genetic Material Scientists knew that chromosomes were involved in the transmission.
DNA: The Genetic Material
Roles of Enzymes in DNA Replication
1  Walter Sutton discovered chromosomes were made of DNA and Protein  However, scientists were NOT sure which one (protein or DNA) was the actual genetic.
The Structure of DNA Ag Biology. What is DNA? Deoxyribonucleic AcidDeoxyribonucleic Acid Structure that stores hereditary materialStructure that stores.
DNA: The Genetic Material. Identifying the Genetic Material Experiments of Griffith and Avery yielded results that suggested DNA was genetic material.
Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu DNA: The Genetic Material Chapter 9 Table of Contents Section 1.
Chapter 9 Section 3 The Replication of DNA.
DNA: The Genetic Material. The Structure of DNA The Replication of DNA.
DNA: The Genetic Material. DNA Deoxyribonucleic Acid.
Chapter 9 Sections 9-1 and 9-2.
Deoxyribonucleic Acid DNA. Organism Cell Chromosome Gene DNA Nucleotide.
Important Experiments Griffith’s Experiments In 1928, when trying to prepare a vaccine against a pneumonia-causing bacterium, Griffith discovered TRANSFORMATION.
The History of DNA. 1.Griffith- experiment showed that live uncoated bacteria acquired the ability to make coats from dead coated bacteria. He called.
DNA: The Genetic Material Coach Fults Chapter 9. Transformation Mendel’s work answered why we resemble our parents But what are those genes made of?
Chapter 12: DNA Mr. Freidhoff 1900’s What is known to man? – Chromosomes carry genetic information. – Some type of heredity is passed on to offspring.
DNA Chapter 12 DNA. Mendel’s work and experiments created more questions and sparked scientists to start researching heredity with a more molecular approach.
DNADNA: The Blueprint of Life History Structure & Replication.
Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Overview Section 2 The Structure of DNA DNA.
CHAPTER 12 DNA Identifying the Substance of Genes Griffith was trying to find a vaccine for Streptococcus pneumoniae. Worked with two types or strains.
Chapter 9-The Genetic Material 1928-Griffith preparation of a vaccine. Let’s look at Figure 2-page 191 Vaccine-A substance that is prepared from killed.
Chapter 9 Table of Contents Section 1 Identifying the Genetic Material
DNA, RNA and Proteins The Structure of DNA
DNA: The Genetic Material
DNA and Replication.
Section 1: The Structure of DNA
9.2 and 9.3 The Structure and Replication of DNA 9.2 Objectives
DNA and Replication.
DNA Deoxyribonucleic Acid
Chapter 9 Section 2 The Structure of DNA.
Chapter 9 Section 2 The Structure of DNA.
DNA: The Genetic Material
12.1 DNA.
DNA and Replication.
Chapter 9 Section 3 The Replication of DNA.
DNA Deoxyribonucleic Acid
Structure of DNA and Replication
DNA and Replication.
Griffith’s Experiments
DNA Structure Standard 3.1.1
Presentation transcript:

In 1928, Frederick Griffith, a bacteriologist, was trying to prepare a vaccine against pneumonia

Griffith’s Experiments A vaccine is a substance that is prepared from killed or weakened disease-causing agents, including certain bacteria The vaccine is introduced into the body to protect the body against future infections by the disease-causing agent

Griffith discovered that harmless bacteria could turn virulent when mixed with bacteria that cause disease A bacteria that is virulent is able to cause disease Griffith had discovered what is now called transformation, a change in genotype caused when cells take up foreign genetic material

Griffith’s Discovery of Transformation

Viral Genes and DNA In 1952, Alfred Hershey and Martha Chase used the bacteriophage T2 to prove that DNA carried genetic material A bacteriophage is a virus that infects bacteria When phages infect bacterial cells, they are able to produce more viruses, which are released when the bacterial cells rupture

DNA’s Role Revealed Hershey and Chase carried out the following experiment Step 1 T2 phages were labeled with radioactive isotopes Step 2 The phages infect E. coli bacterial cells. Step 3 Bacterial cells were spun to remove the virus's protein coats

Hershey and Chase concluded that the DNA of viruses is injected into the bacterial cells, while most of the viral proteins remain outside The injected DNA molecules causes the bacterial cells to produce more viral DNA and proteins This meant that the DNA, rather than proteins, is the hereditary material, at least in viruses.

By the early 1950’s, most scientists were convinced That genes were made of DNA. The problem is that no one knew what it looked like. Then along came James Watson & Francis Crick.

James Watson and Francis Crick

A Winding Staircase Watson and Crick determined that a DNA molecule is a double helix—two strands twisted around each other, like a winding staircase. Nucleotides are the subunits that make up DNA. Each nucleotide is made of three parts: a phosphate group, a five-carbon sugar molecule, and a nitrogen-containing base

The five-carbon sugar in DNA nucleotides is called deoxyribose Structure of a Nucleotide

DNA Double Helix

The nitrogen base in a nucleotide can be either a bulky, double-ring purine, or a smaller, single-ring pyrimidine.

Discovering DNA’s Structure Chargaff’s Observations In 1949, Erwin Chargaff observed that for each organism he studied, the amount of adenine always equaled the amount of thymine (A=T) Likewise, the amount of guanine always equaled the amount of cytosine (G=C). However, the amount of adenine and thymine and of guanine and cytosine varied between different organisms

Wilkins and Franklin’s Photographs In 1952, Maurice Wilkins and Rosalind Franklin developed high-quality X-ray diffraction photographs of strands of DNA These photographs suggested that the DNA molecule resembled a tightly coiled helix and was composed of two or three chains of nucleotides

X-Ray Diffraction

Watson and Crick’s DNA Model In 1953, Watson and Crick built a model of DNA with the configuration of a double helix, a “spiral staircase” of two strands of nucleotides twisting around a central axis The double-helix model of DNA takes into account Chargaff’s observations and the patterns on Franklin’s X-ray diffraction photographs.

Pairing Between Bases An adenine on one strand always pairs with a thymine on the opposite strand, and a guanine on one strand always pairs with a cytosine on the opposite strand These base-pairing rules are supported by Chargaff’s observations The strictness of base-pairing results in two strands that contain complementary base pairs

In the diagram of DNA below, the helix makes it easier to visualize the base-pairing that occurs between DNA strands

When the double helix was discovered, scientists were very excited about the complimentary relationship between the sequences of nucleotides. Watson and Crick proposed that one DNA strand serves as a template on which the other strand is built.

Roles of Enzymes in DNA Replication The complementary structure of DNA is used as a basis to make exact copies of the DNA each time a cell divided. The process of making a copy of DNA is called DNA replication DNA replication occurs during the synthesis (S) phase of the cell cycle, before a cell divides DNA replication occurs in three steps

Step 1- DNA helicases open the double helix by breaking the hydrogen bonds that link the complementary nitrogen bases between the two strands. The areas where the double helix separates are called replication forks

Step 2 - At the replication fork, enzymes known as DNA polymerases move along each of the DNA strands. DNA polymerases add nucleotides to the exposed nitrogen bases, according to the base-pairing rules Step 3 - Two DNA molecules that form are identical to the original DNA molecule

Checking for Errors In the course of DNA replication, errors sometimes occur and the wrong nucleotide is added to the new strand. An important feature of DNA replication is that DNA polymerases have a “proofreading” role This proofreading reduces errors in DNA replication to about one error per 1 billion nucleotides

The Rate of Replication Replication does not begin at one end of the DNA molecule and end at the other The circular DNA molecules found in prokaryotes usually have two replication forks that begin at a single point The replication forks move away from each other until they meet on the opposite side of the DNA circle

In eukaryotic cells, each chromosome contains a single, long strand of DNA Each human chromosome is replicated in about 100 sections that are 100,000 nucleotides long, each section with its own starting point With multiple replication forks working in concert, an entire human chromosome can be replicated in about 8 hours

Replication Forks