DNA - Structure and Function and Watson and Crick

Facts About Your DNA
Inside every cell in your body there is a nucleus that contains your genetic material. That genetic material is deoxyribonucleic acid – DNA for short. Your DNA controls many of the things about you, but scientists still are not sure about the exact role of nature (your genes) and nurture (how you were raised) in making you who and what you are.

Here are some facts:

1. Almost every cell in your body contains about 2.91 billion DNA.
2. The DNA is divided into two sets of 23 chromosomes.
3. You get one set of chromosomes from your mother and one set from your father.
4. Every time your cells divide, the information is copied and divided into the new cells. Every time those chromosomes are passed on from mother or father, they are recombined to make unique chromosomes — YOUR chromosomes.

Nucleotides and the Structure of DNA

1. Structurally, DNA is made up of nucleotides.
2. A nucleotide is made up of a sugar, a phosphate and a base.
3. Nucleotides hook together to make the sugar-phosphate backbone of every strand of DNA.
4. The bases pair up with opposite matching bases on the other strand of DNA that makes up the “double-helix” structure.
5. The pairs are linked by weak hydrogen bonds.
6. There are four kinds of nucleotides or “base pairs” -- A for adenine, T is for thyamine, G is for guanine and C is for cytosine.  A always pairs with T. G always pairs with C.
7. They are linked together (the two strands of DNA) and stacked like a ladder who’s sides spiral around each other into their famous double helix shape.

In 1953 James Watson and Francis Crick built the first correct structural model of DNA.  They used scale models of atoms to work out their theories about how the structure was set up. When they discovered how the base pairs Adenine fit together with Thymine and Guanine fit together with Cytosine, they knew they had found a solution to DNA’s structural puzzle.
   
Each nitrogenous base pair was held together by a weak hydrogen bond and stacked flat on top of each other like steps. To each base pair, a two sugar-one phosphate complex attached. This formed the so-called nucleic acid. But what made the structure come together in perfect harmony was how the two strands of DNA, that made the double helix, were discovered to wind in opposite directions. This set up of matching base pairs makes DNA well suited for replication. 

The DNA model built by Watson and Crick and the accompanying paper published in Nature, showed how DNA’s base pair structure is suited for the copying of genetic material. In 1962 they, along with Maurice Wilkins, received the Nobel Prize for Physiology for their work.

One April 24, 2003, scientists at the National Human Genome Research Institute (NHGRI) and the US Department of Energy (DOE) announced that they had completed the sequencing of the human genome, 50 years to the day that Nobel Prize winners James Watson and Francis Crick published the molecular structure of the DNA double helix. The decoding of the 3 billion DNA letters of the human genome is the result of one of the most ambitious scientific projects of all time, comparable to going to the moon and splitting the atom. This amazing achievement was accomplished by The International Human Genome Sequencing Consortium and included hundreds of scientists at 20 sequencing centers in the United States, Great Britain, China, France, Germany, Japan and China. These scientists recognized that the sequence of the human genome belonged to every human being and placed all of the sequence generated by the Human Genome Project into public databases freely available to scientists around the world with no restrictions on its use.

Collaborative consultation on website genetics and genomics from Dr. Stephen M. Carleton, Assistant Professor, Department of Anatomy and Cell Biology, SUNY Health Science Center at Brooklyn.