Download DNA Structure _ ReplicatonNC

1. What structure carries genetic
information from generation to
generation?
2. Which organelle is this structure
located in?
3. How long do you think it has taken to
discover DNA and its structure? Do you
think one person is responsible for the
discovery?
DNA is the GENETIC or HEREDITARY material.
In other words, DNA is what gets “passed
down” to future generations that causes us
to have many of the traits we have.
Many important scientists contributed to
the discoveries:
Gregor Mendel
• “Father of Genetics” (1822-1884)
• Famous experiments with pea plants that
explained patterns of inheritance
• Two “units” of information- one from each
parent
• First scientist to acknowledge material for
heredity
Frederick Griffith 1928
Fred was trying to find a vaccine against
pneumonia, but instead made a
breakthrough in world of heredity.
Frederick experimented with pneumonia in
mice and found that a hereditary material
caused pneumonia.
Oswald Avery, 1944
Determined which molecules in cells caused
pneumonia to occur.
He separated all organic compounds inside of the
cells and found only the DNA caused the disease.
*******Conclusion: DNA must be the hereditary material
Alfred Hershey &
Martha Chase,
1952
• Skeptical of other
scientists’
experiments
• Wanted to be sure
DNA was
hereditary
material
Rosalind Franklin,
1952
• Studied structure of many
microscopic viruses and
cellular structures
• Researched DNA – used XRAY Diffraction to show shape
of DNA= helical w/ 2 strands.
• Rosalind’s lab work was stolen
James Watson &
Francis Crick,
1953
Watson and Crick’s model of DNA was a
DOUBLE HELIX,
in which two strands were wound around
each other.
The sides of the DNA
“ladder” are made of
SUGARS and
PHOSPHATES.
So, DNA is said to have a
SUGAR-PHOSPHATE
BACKBONE.
The rungs of the DNA
“ladder” are made of a
sequence of four
chemicals called
NITROGENOUS BASES.
Erwin Chargaff,
in the early 1900s,
discovered that
certain chemicals in
all DNA seemed to be
present in almost
EQUAL amounts.
ADENINE and THYMINE
were always present
in equal amounts.
GUANINE and
CYTOSINE were
always present in
equal amounts.
THE BASE PAIRING RULE:
Adenine [A] always pairs with Thymine [T]
Guanine [G] always pairs with Cytosine [C]
THE BIG PICTURE
All living things are made of cells...
onion root tip
THE BIG PICTURE
Each individual cell has a NUCLEUS, or at
least a NUCLEAR REGION...
nucleus
THE BIG PICTURE
Each cell’s nucleus contains the
CHROMATIN...
THE BIG PICTURE
The chromatin is composed of
deoxyribonucleic acid, or DNA...
DNA
chromatin
THE BIG PICTURE
DNA is composed of a deoxyribose sugars,
phosphates, and paired nitrogenous
bases...
Sugarphosphate
backbone
Nitrogenous
base pairs
THE BIG PICTURE
The nitrogenous bases match up
according to the BASE PAIRING RULE,
A goes with T and C goes with G