Griffith and Transformationkellywms.weebly.com/uploads/5/4/9/0/54901139/dna_history_and_st… ·...
16
End Show 12–1 DNA Slide 1 of 37 Copyright Pearson Prentice Hall Griffith and Transformation 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.
Transcript of Griffith and Transformationkellywms.weebly.com/uploads/5/4/9/0/54901139/dna_history_and_st… ·...
End Show
12–1 DNA
Slide
1 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
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.
End Show
12–1 DNA
Slide
2 of 37
Copyright Pearson Prentice Hall
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.
End Show
12–1 DNA
Slide
3 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
Griffith's Experiments
Griffith set up four
individual experiments.
Experiment 1: Mice
were injected with the
disease-causing strain
of bacteria. The mice
developed pneumonia
and died.
End Show
12–1 DNA
Slide
4 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
Experiment 2: Mice were
injected with the harmless
strain of bacteria. These
mice didn’t get sick.
Harmless bacteria
(rough colonies)
Lives
End Show
12–1 DNA
Slide
5 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
Experiment 3: Griffith
heated the disease-
causing bacteria. He then
injected the heat-killed
bacteria into the mice.
The mice survived.
Heat-killed disease-
causing bacteria (smooth
colonies)
Lives
End Show
12–1 DNA
Slide
6 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice.
What do you predict
will happen? Write
down your prediction
on your paper.
End Show
12–1 DNA
Slide
7 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
Results of Experiment 4: The mice developed pneumonia and died.
Why did this happen?
Live disease-
causing bacteria
(smooth colonies)
Dies of pneumonia
Heat-killed disease-
causing bacteria
(smooth colonies)
Harmless bacteria
(rough colonies)
End Show
12–1 DNA
Slide
8 of 37
Copyright Pearson Prentice Hall
Griffith and Transformation
Griffith concluded that some factor in cells must contain information that could change harmless bacteria into disease-causing ones. He called this process transformation.
Live disease-
causing bacteria
(smooth colonies)
Heat-killed disease-
causing bacteria
(smooth colonies)
Harmless bacteria
(rough colonies)
Dies of pneumonia
End Show
12–1 DNA
Slide
9 of 37
Copyright Pearson Prentice Hall
Avery and DNA
Avery and DNA
Oswald Avery repeated Griffith’s work to determine
which molecule was most important for
transformation.
He used enzymes to destroy proteins, lipids,
carbohydrates, and other molecules, including the
nucleic acid RNA.
Transformation still occurred.
End Show
12–1 DNA
Slide
10 of 37
Copyright Pearson Prentice Hall
Avery and DNA
Avery and other scientists repeated the experiment
using enzymes that would break down DNA.
When DNA was destroyed, transformation did not
occur. Therefore, they concluded that DNA was the
transforming factor.
DNA stores and transmits the genetic information
from one generation of an organism to the next.
End Show
12–1 DNA
Slide
11 of 37
Copyright Pearson Prentice Hall
The Components and Structure of DNA
The Components and Structure of DNA
DNA is made up of nucleotides.
A nucleotide is a monomer of nucleic acids made
up of:
•Deoxyribose – 5-carbon Sugar
•Phosphate Group
•Nitrogenous Base
End Show
12–1 DNA
Slide
12 of 37
Copyright Pearson Prentice Hall
The Components and Structure of DNA
There are four kinds of bases in in DNA:
• adenine
• guanine
• cytosine
• thymine
End Show
12–1 DNA
Slide
13 of 37
Copyright Pearson Prentice Hall
The Components and Structure of DNA
Chargaff's Rules
Erwin Chargaff discovered that:
• The percentages of guanine [G] and cytosine
[C] bases are almost equal in any sample of
DNA.
• The percentages of adenine [A] and thymine
[T] bases are almost equal in any sample of
DNA.
End Show
12–1 DNA
Slide
14 of 37
Copyright Pearson Prentice Hall
The Components and Structure of DNA
X-Ray Evidence
Rosalind Franklin used X-ray
diffraction to get information
about the structure of DNA.
She aimed an X-ray beam at
concentrated DNA samples
and recorded the scattering
pattern of the X-rays on film.
End Show
12–1 DNA
Slide
15 of 37
Copyright Pearson Prentice Hall
The Components and Structure of DNA
The Double Helix
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.
End Show
12–1 DNA
Slide
16 of 37
Copyright Pearson Prentice Hall
The Components and Structure of
DNA
DNA Double Helix
