This is a blog that I do in my biology class. It is mostly about the current science-y things that are going on. Enjoy. :)
Monday, May 16, 2011
Race for the Double Helix
Throughout the past two days our biology class watched the movie “The Race for the Double Helix”. It is the story of how James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkens came to discover the double helix in DNA.
After reading the 1953 article of what the scientists came about when they found the double helix, answered a lot of different questions. One of those questions would be the significance of the structure of the double helix. The significance would be that the structure has two helical chains coiled around the same axis. The two chains are related by a dyad perpendicular to the fibre axis. Both of the chains follow to the right of the helix and the phosphates that are on the outside. The structure overall is an open one and the water content was high and the two chains are held together by purine and pyrimidine basis. And they have a certain ration which is 1:1:6:6. This is significant because it was different than anything the scientists even thought of back in the early 1900s. And having Watson and Crick find this was truly an astounding scientific event.
The triple helix didn’t work because DNA actually only has two helix’s. The triple helix would’ve never worked due to the fact that they phosphates were arranged on the outside and the bases on the inside and they were linked together by the hydrogen bonds. And when they took X-rays of it they saw a salt and not a free acid. Without the free acid the structure would not hold together.
The novel feature of the Watson - Crick Model is that the structure had two helical chains each coiled around the same axis. Both of the chains follow right helices and maintain the same sequence. The phosphates are on the outside of the helix and the sugars near the base. And since the phosphates are on the outside the cations have easy access to them. And since the structure is an open one, the water content is high. The main thing, though, is that the two chains are held together by purine and pyrimidine bases.
The sequence of one side of DNA determines the other side because there are two sets of pairs. A – T and C – G. So if one side is ACGT then the other would be TGCA. They can only pair with each other, thus determining the other side’s DNA format.