DNA Structure
- Chargoff discovered ATCG that are connected to a sugar base.
- Phosphates also connect the sugar bases together to form the DNA "backbone"
- Watson and Crick didn't do any experiments but they used other people's work to put together the big picture and discover the structure of DNA
- Roslind Franklin's X-ray crystallography gave W & C the final piece they needed to make their discovery. Below you can see the picture that Franklin took of a strand of DNA. This picture showed W & C that DNA wraps around in a double helix.
Youtube Vid
http://www.youtube.com/watch?v=tknYrU98rBk&feature=related
Franklin's X-ray Crystallography
- Opposite strands of DNA run different ways. This is the only way that A-T and C-G's can line up correctly.
- Below you can see this Anti-Parallelism
Anti-Parallelism .
Quick Facts
a) DNA Nucleotides have a deoxyribose sugar, phosphate group and a nitrogenous base: Adenine, Thymine, Cytosine, Guanine
b) Nucleotides chain together, the 5’ phosphate group of one nucleotide adding to the 3’OH on the sugar end of another. Two chains hydrogen bond together via the bases. 2 bonds between A and T ; 3 bonds between C and G. The two chains run antiparallel due to the way the bases bond.
b) Nucleotides chain together, the 5’ phosphate group of one nucleotide adding to the 3’OH on the sugar end of another. Two chains hydrogen bond together via the bases. 2 bonds between A and T ; 3 bonds between C and G. The two chains run antiparallel due to the way the bases bond.
Blackboard Questions
- In the 60 years following the determination of the structure of DNA by Watson and Crick there has been an extraordinary explosion of information and application related to DNA. What was it about knowing the structure of DNA that led us to such quick discoveries related to DNA replication and Protein Synthesis? In other words, how are the Structure of DNA and Function of DNA so intimately tied - or how does the knowledge of DNA structure make it possible to understand DNA function?
- Watson and Cricks discovery was so important to the scientific expansion of knowledge about DNA and inheritance because of the structure of the double helix. The picture taken by Rosalind Franklin that shows the double helix nature shows us that the outside of DNA is always the same. The only thing different about one set of DNA with another is the order of the ATCG’s. The Structure of DNA directly relates to the function of DNA because it showed us that the genetic code is based on the order of the nucleotides. This opens up a realm of possibilities pertaining to all sorts of medical and scientific advances that pertain to DNA. The human genome would never have been accomplished if the structure of DNA were never discovered.