- DNA has a double helix shape, with bas pairs (A, T, C, G) joined by hydrogen bonds.
- RNA is single stranded
- Can form a double helix by itself, but usually doesn’t.
- 3 main parts of DNA and RNA:
- phosphate linking group
- nucleic acid base → reflects changes of A/T/C/G
- sugar group
- Differences between DNA and RNA:
- RNA uses Uracil instead of Thymine
- They’re chemically very similar
- DNA has H at 2’, RNA has OH at 2’
- Nucleotides link via a condensation reaction (produces H2O) between phosphate and sugar (sugar-phosphate backbone).
- Why do we have both DNA and RNA?
- DNA is much more stable.
- Lack of oxygen in DNA makes it energy intensive to replicate.
- But DNA can still self-replicate.
- RNA World hypothesis: all genetic information was once stored in RNA.
- Start simple and evolve to be more complex.
- This was during pre-cellular times.