Fill in the Blanks who deserves credit for discovering the structure of the doub

Question

Fill in the Blanks

who deserves credit for discovering the structure of the double helix? The famous model of DNA was buit by Watson and Crick in 1953 to demonstrate the secondary structure of DNA. This was not the first attempt at modeling DNA'Ds structure, however. Before 1953, there were several failed attempts. The accumulation of data from different research groups was key to arriving at the correct model. What were the incorrect versions of DNA structure, and how did Watson and Crick get it right? Part A In the 1950s, the race to solve the secondary structuire of DNA became intense. In an uncharacteristic rush to publish, Linus Pauling erroneously proposed a triple-stranded structure in February 1953. This model had the nitrogenous bases orn the exterior and the sugar phosphate backbones clustered in the middle How does he orientation of the sugar phosphate backbone in this model compare with the one proposed by Watson and Crick? Do you think Pauling s structure could exist in cells? Why or why not? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Reset Help away from would toward would not had Watson and Crick s model the sugar-phosphate backbones oriented the exterior. Pauling's structure lkely exist in cells because the sugar-phosphate backbones of nucleic acids are one another charged and would repel negatively had not positively

Explanation / Answer

Part A:

The triple stranded structure had the base molecules located outside of the molecule and the sugar-phosphate groups clustered inside. The problem that they faced was about fitting all the negatively charged phosphates into the core without blowing up the whole structure.They were thus looking for positively charged ions that could cancel out the negatively charged phosphates and fit into the core. Magnesium and Calcium ions were consisdered to be possibilities, but Rosalind Franklin pointed out that any positively charged particle in the core would be surrounded by water making them neutral. This would not help in negating the negatively charged phosphates. Proving her point, she noticed that DNA soaks up a lot of water indicating sugar-phosphate groups to be present outside of the molecule. This proves that Pauling's structure of DNA cannot be present in any cells.

Watson and Crick's model HAD the sugar-phosphate backbones oriented TOWARD the exterior. Pauling's structure WOULD NOT likely exist in cells because the sugar-phosphate backbones of nucleic acids are NEGATIVELY charged and would repel one another.

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