Which of the following did watson and crick already know when they were trying to determine the structure of dna? The number of .

Purines is equal to the number of Pyrimidines.

Explanation:

Watson and Crick have already found this fact that there are four nitrogenous bases namely Adenine, Guanine, Thymine and Cytosine are found in DNA. In these four the first two are Purines and the later two are Pyrimidines. They had also found the manner of pairing of these bases that Adenine pairs with Thymine via double hydrogen bonds and Guanine pairs with Cytosine via three hydrogen bonds.

After getting all these data they used X-Ray Crystallography to visualize the double helix structure of DNA. After this experiment they further reported other properties like bond angles, grooves, number of bases per turn etc. of the DNA.

1. desertification

2. captive breeding

3. black rhinoceros

4. renewable resources

explanation:

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