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Watson and Crick’s double helix model of DNA
Let me introduce
myself………….
………
(b. April 6, 1928, Chicago, Ill., U.S.),
American geneticist and biophysicist
who played a crucial role in the
discovery of the molecular structure of
deoxyribonucleic acid (DNA), the
substance that is the basis of heredity.
James D. Watson
In my
turn………
(b. June 8, 1916,Northampton,
Northamptonshire,
Eng.),
British
biophysicist,who,with
James
Watson.During
World War II, Crick interrupted
his education to work as a
physicist,but afterward he
turned to biology at the
Strangeways.
Francis H.C. Crick
Then I will describe watson’s
and my DNA model………….
The DNA model contains the
actual metal plates used by
James Watson and Francis
Crick to determine the
molecular structure of DNA in
1953.
Constructed out of metal plates
and rods arranged helically
around a retort stand, the
model shows one complete
turn of the famous double helix.
The metal plates represent the
four bases whose
complementary arrangement
immediately suggested a
possible copying mechanism
for the genetic material.
……..
Let’s talk about our
discovery of DNA
Drs. Watson and Crick
& The Discovery of DNA's Double
Helix
In 1954, Dr James Watson and Dr Francis Crick
identified the structure of DNA, the cellular material
that carries genetic codes. They found that DNA is
made up of two protein strands connected by a
phosphate backbone, forming what they termed the
"double helix." Watson and Crick's discovery of the
double helix laid the foundation for the study of
genetics and the development of biotechnology.
What are DNA
and
Chromosomes…
…Crick??
it’s easy for me to
explain
these,watson,first
………
DNA & Chromosomes
DNA
DeoxyriboNucleic Acid is commonly
known as DNA. Originally discovered
by Francis Crick and James Watson,
the shape of DNA is a double helix.
The composition of DNA is a series of
nitrogenous bases and sugar and
phosphate strands. Within the ladder
model of DNA, the sugar and
phosphate strands compose the
sides of the DNA model, or molecule,
while the actual rungs of the ladder
are made up of the 4 nitrogen bases.
Chromosomes
Chromosomes are the package for
DNA and genes. To contain the
DNA within the nucleus of a cell,
the genetic information is wound
up into strands like coiled rope.
These strands take the shape of
X's. The genetic information a
chromosome holds, or one piece
of genetic information a
chromosome can hold, is known
as a gene.
What about
the order of
gene code…..?
The order of gene code
Primarily, it had to be understood
that four nucleotide bases
existed: adenine (A), guanine
(G), cytosine (C), and thiamine
(T) .By using Chargaff’s
research, restrictions were
established about the
nucleotide sequencing and it
was proven that A—T, T—A,
C—G, and G—C were the only
bonds. The pairing of the
bases in this fashion was
advantageous as Watson and
Crick noted the pairs all
measured a uniform width and
could all easily fit into the
frame of the double helix.
Yeah!!!!!!!!In the final,there are
four things I must add and you
need to understand…..
Figure 1: Portion of polynucleotide chain of deoxyribonucleic acid (DNA).
The inset shows the corresponding pentose sugar and pyrimidine base in
ribonucleic acid (RNA).
Figure 2: The bases of one helical strand in DNA are paired with
complementary bases of the other strand by hydrogen bonds:
adenine (A) is paired with thymine (T) and cytosine (C) is paired with
Figure 3: A possible method for the replication of DNA according to
Watson and Crick. The arrows indicate the direction of rotation.
Figure 4:DNA base’s molecular structure is a small amount of negative electrical charge
on nitrogen and oxygen atoms that are not attached to a hydrogen atom, a positive
charge exists on those atoms that are attached to hydrogen.Adenine has surplus
negative charge, thiamine has surplus positive charge.
This is the end of our
presentation,bye
bye