• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Structure of DNA

Extracts from this document...


Structure of DNA DNA is the code for life, the key to unlocking this code lies in the structure of DNA. Many different people have been involved in the discovery of the structure of DNA, and many different ideas have been discussed. Francis Crick and James Watson have made a momentous discovery about the structure of DNA, but where did their ideas originate and where will they lead? Early ideas about DNA came in 1951 from Rosalind Franklin who was an X-ray crystallographer. She suggested that DNA had a helical structure and that the phosphate groups of the nucleic acids were positioned on the outside of the chain. She also thought that each helical unit had 2,3 or 4 nucleic acid chains. ...read more.


In 1952 Franklin responded to Watson and Crick's findings by dismissing the helical structure that she had initially proposed. She also dismissed the way in which the phosphate groups were held together. If they were held together with Mg++ ions then tight shells of water molecules would surround them. IN 1952/1953 Linus Pauling a successful chemist based his theories on the main features of the X-ray diagram. He claimed that DNA was made up of three intertwined helical polynucleotide chains. The phosphate groups are closely packed about the axis of the molecule, with purine and pyrimidine groups projecting radially with their planes being perpendicular to the molecular axis. In 1953 Watson responded to Paulings ideas by saying that the phosphate groups in Pauling's model were not ionised, but that each group contained a bound hydrogen atom and so had no overall charge. ...read more.


The triple helix structure would be very tight allowing little opportunity for change in positions of the atoms. In 1953 Watson and Crick published a paper in which they discussed the structure of DNA. Their structure was different to those initial ideas. It consisted of two helical chains each coiled round the same axis. Both chains followed right-handed helices but the sequences of the atoms in the two chains run in opposite directions. The bases are on the inside of the helix and the phosphates are on the outside. The purine and pyrimidine bases hold the chains together. The planes of the bases are perpendicular to the fibre axis. They are joined together in pairs by hydrogen bonds. One of the pair must be a Purine and the other a pyramidine for bonding to occur. The base Adenine (purine) joins with Thymine (pryimidine) and Guanine (purine) with Cytosine (pyrimidine). ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Genetics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Genetics essays

  1. What are the advantages and disadvantages of using DNA sequence data for assessing relationships ...

    The problem with using outgroups is that they are all subject to long branch attrition artefacts, reducing reliability, and the choice of outgroup, being subjective. Because DNA sequencing can only be reliably used on extant species the construction of the tree runs into another obstacle.

  2. DNA Fingerprinting: A review of the criticisms of DNA evidence. Is it really the ...

    And whilst population studies have shown that there exist significant differences in the frequency of genes between ethnic groups, other studies have shown that there are a lot of similarities in all populations.33 However, it has been proved that the differences in the frequency of genes are much more than the similarities34.

  1. How hair and fibre aid in the investigation of crime.

    abducted in Ohio and her body was found six days later- strangled and raped. Distinctive orange fibres were found in her hair which looked like the ones found on a 12 year old murdered female, eight months ago. The evidence was concluded to be carpet fibres due to the odd shape and was analysed to be polyester.

  2. Blood Factors and the DNA Fingerprint.

    Every cell in an individual's body contains identical DNA. Fingerprints come only from fingers, but DNA can be found in blood, in urine, in feces, in saliva, in some hair, in the shed skin cells found in a facecloth or toothbrush, even the sweatband of a hat (http://www.ncjrs.org/nij/DNAbro/id.html).

  1. Using DNA to Solve Crimes.

    (4) Professionals working in the criminal justice system need additional training and assistance in order to ensure the optimal use of DNA evidence to solve crimes and assist victims. President Bush believes we must do more to realize the full potential of DNA technology to solve crime and protect the innocent.

  2. The Integration of DNA Applications in Forensic Science

    Then, the same blood sample is typed with a PGM enzyme system and yields a type 1+ factor, a 19% frequency. When calculated the percentage of possible donors of the sample obtained from an elected ethnic population, Caucasian, with type 1+ A blood is: 35% x 19% = 6.7%.

  1. Watson, Crick or Franklin… Who Really Discovered the Secret of DNA?

    Meanwhile at King's College in London, Maurice Wilkins and Rosalind Franklin were also studying DNA. The Cambridge team's approach was to make physical models to narrow down the possibilities and eventually create an accurate picture of the molecule. The King's team took a more experimental approach, looking particularly at x-ray diffraction images of DNA.

  2. Compare the structure of RNA and DNA

    Another function of DNA is protein synthesis. Proteins are made of amino acids. Proteins are characterized by the sequence of amino acids in their structure. This sequence is controlled and dictated by DNA. Proteins have many important functions in the body, and the type of proteins an organism synthesizes characterizes that organism.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work