Structure of DNA
The Structure of DNA
1. The Double Helix
- 2 polynucleotide chains (or DNA strands) twisted around each other to form a double helix
- The 2 strands are antiparallel (run in opposite directions: 5' to 3' and the other, 3' to 5' end)
- Held together by hydrogen bonds between nitrogenous bases of opposite strands (complementary base pairing)
2. Complementary base pairing
- The pairing of a purine and pyrimidine by formation of hydrogen bonds
- A forms 2 bonds with T, C forms 3 bonds with G
- Ratio of A:T=1:1, C:G=1:1 (for obvious reasons) So why does RNA have screwed up ratios? Beause it exists as a single strand, thus complementary base pairing cannot occur.
3. Measurements just know point 1
- Each complete turn has 10 base pairs
- Each complete turn spans 3.4nm
- Width of a base: 1nm (constant width throughout the sugar-phosphate backbones is 2nm then.)
4. Differences between DNA and RNA
- Read page 10 of your notes! Lol. In fact read everything from page 10 onwards.
I hope all that was useful for your foundation for DNA.
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