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6. Adenine pairs with thymine, there are 2 hydrogen bonds between them.

7. Guanine pairs with cytosine, there are 3 hydrogen bonds between them.

8. The 2 bases that are purines are : adenine and guanine

9. The 2 bases that are pyrimidines are : thymine and cytosine

10. Purines can’t bond with purines and pyrimidines can’t bond with pyrimidines because there is not enough space for two purines to fit within the helix and too much space for two pyrimidines to get close enough together for hydrogen bonds to form between them.

Explanation:

The answers are in order from 6 to 10.

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