Summary
Nucleic acids like DNA and RNA are macromolecules made of nucleotides, which consist of a nitrogenous base, a pentose sugar, and a phosphate group. DNA is structured as a double helix with antiparallel strands, while RNA is single-stranded and contains uracil instead of thymine.
- Nucleotide — the building block of nucleic acids. Example: Consists of a nitrogenous base, a pentose sugar, and a phosphate group.
- Purines — nitrogenous bases with a double ring structure. Example: Adenine and guanine.
- Pyrimidines — nitrogenous bases with a single ring structure. Example: Cytosine, thymine, and uracil.
- Semi-conservative DNA Replication — a process where each new DNA molecule retains half of the original molecule. Example: Involves enzymes like helicase and DNA polymerase.
Exam Tips
Key Definitions to Remember
- Nucleotide
- Purines and Pyrimidines
- Semi-conservative DNA Replication
Common Confusions
- Confusing purines with pyrimidines
- Mixing up the structure of DNA and RNA
Typical Exam Questions
- What is the structure of a nucleotide? A nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group.
- How does DNA replicate semi-conservatively? Each new DNA molecule retains one original strand and one new strand.
- What is the difference between DNA and RNA? DNA is double-stranded and contains thymine, while RNA is single-stranded and contains uracil.
What Examiners Usually Test
- Understanding of complementary base pairing
- Differences between DNA and RNA
- Steps involved in DNA replication