Question

question 3
describe the directionality of dna

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question 4
explain how rosalind franklins x - ray crystallography work helped watson and crick in their quest to determine the physical structure of dna.

Explanation:

For Question 3: DNA has a 5'-to-3' directionality. The 5' end has a phosphate group attached to the 5 - carbon of the deoxyribose sugar, and the 3' end has a hydroxyl group on the 3 - carbon of the deoxyribose sugar. DNA polymerases add nucleotides only to the 3' end during replication.
For Question 4: Rosalind Franklin's x - ray crystallography images, like Photo 51, provided crucial data. The images showed the helical nature of DNA, the spacing between the bases, and the overall dimensions of the molecule. This information was essential for Watson and Crick to build their accurate double - helix model of DNA.

Answer:

Question 3: DNA has 5'-to-3' directionality.
Question 4: Her x - ray crystallography images showed DNA's helical nature, base spacing, and dimensions, aiding Watson and Crick in building the double - helix model.