DNA (deoxyribonucleic acid) is the molecule that stores genetic information in all living organisms. Understanding DNA structure is essential for lear
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What is the difference between a purine and a pyrimidine?
Purines (adenine and guanine) have two rings: a 6-membered ring fused to a 5-membered ring. Pyrimidines (cytosine and thymine) have only one 6-membered ring. Purines are larger than pyrimidines. In DNA, a purine (A or G) always pairs with a pyrimidine (T or C) respectively, maintaining uniform width of the double helix.
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Why are there more hydrogen bonds between G and C than between A and T?
Guanine and cytosine form three hydrogen bonds, while adenine and thymine form two hydrogen bonds. Regions of DNA with more G-C pairs are more stable (higher melting temperature) because three hydrogen bonds are stronger than two. This is used in laboratory techniques to denature and reanneal DNA.
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What is semiconservative DNA replication?
During replication, each original strand (parent strand) remains intact and serves as a template for a new complementary strand. The result is two DNA molecules, each containing one original parent strand and one newly synthesized strand. This is called semiconservative because half (semi) of each new DNA molecule is conserved from the original.
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