Learn About DNA Structure

Uncovering the structure of DNA has proven to be vital to our understanding of DNA and its importance and relevance to our lives. The contributions by Watson, Crick and numerous other scientists such as Franklin have allowed for the determination of the structure of DNA. Perhaps even more important are the many applications that have stemmed from our understanding of DNA structure, which stretches to a virtually endless number of areas such as genetic diseases, cancer and our immune systems. It has also allowed scientists to make accurate predictions about many diseases and how they will affect individuals based on their genetic profiles.

Franklin's production of a DNA image was crucial to showing its shape and contributed to the discovery of DNA's double helix by Watson and Crick in the 1950s. The photo was dubbed 'Photo 51' and would ultimately be viewed as a significant aspect in the shaping of our understanding of DNA structure today.

DNA Structure

DNA structure itself is actually quite fascinating, even perhaps to non-scientists! DNA can basically be broken down into smaller parts, which makes its important structure a bit easier to understand. If you can try to picture a helix, you have already got a sense of the structure of DNA. At a very simple level, DNA is a helical structure, with bases that are 'stacked' upon one another. These bases are part of the DNA subunits that are called nucleotides. Each single nucleotide is made up of three parts. They include a:

• Sugar
• Phosphate
• Base

By considering the bases that make up DNA, it can be broken down further. There are four different kinds of bases that are found in a molecule of DNA. Two of the bases are known as purines and two are known as pyrimidines. The naming may sound somewhat lengthy and complicated at first glance but they represent differences in the structures of the bases found in a DNA molecule. The four bases are:

• Adenine (purine)
• Cytosine (pyrimidine)
• Guanine (purine)
• Thymine (pyrimidine)

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Getting a Clear Picture of DNA

To get a clear picture of DNA, it helps if you can imagine two helical chains, with each one coiled around the same axis. Watson and Crick described it well in their published work on DNA and its structure. They explained how the DNA chains travelled in opposite directions, with the bases on the inside of the helix and the phosphates on the outside.

They emphasised the importance of how these two chains are held together by the purine and pyrimidine bases. A purine pairs with a pyrimidine base, which means that one base from a chain is bonded to a single base from the other chain. Ultimately, this means that the two bases lie side-by-side. If you recall the four bases mentioned earlier, you can perhaps understand now how the bases are very specific in how they pair with another base. An adenine base only pairs with thymine and a guanine base only pairs with cytosine. This understanding of the structure of DNA is particularly important because it led to the realisation that if there is an adenine on one side of the pair, then the other base must be thymine. Similarly, if we know there is guanine on one side of the chain, it is paired with cytosine. What this essentially means is that if there is a set sequence of bases on one side of the chain, the other side is automatically determined.

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Important Words from Watson and Crick

After Watson and Crick initially described the structure of DNA, their words have since resonated within the scientific community for decades following the publication of their work on DNA and its structure. After their published work in the British journal Nature described the structure of DNA, they went on to explain that the base pairing that occurs in DNA would seem to suggest a 'copying mechanism' for a person's genetic material. It is this copying mechanism that has been an important part of our understanding of DNA structure in terms of disease and therapeutic treatment today. As such, the words of Watson and Crick have cleared the way for huge strides in our understanding of DNA structure. They have also built the foundation for our knowledge and ability to modify the DNA molecule. In turn, this has allowed us to learn about diseases as well as formulate treatments to reduce morbidity and mortality from disease.

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