Summary
DNA is a macromolecule composed of nucleotides, forming the genetic material in cells. It is structured as antiparallel strands with complementary base pairing, and replicates semi-conservatively.
- Nucleotides — the building blocks of DNA and RNA, consisting of a nitrogenous base, a pentose sugar, and a phosphate group. Example: Adenine, Thymine, Cytosine, Guanine in DNA.
- DNA (Deoxyribonucleic Acid) — a double-stranded polynucleotide with antiparallel strands held together by hydrogen bonds between complementary bases. Example: A pairs with T, and G pairs with C.
- RNA (Ribonucleic Acid) — a single-stranded polynucleotide containing ribose sugar and uracil instead of thymine. Example: mRNA, tRNA, rRNA.
- Adenosine Triphosphate (ATP) — an energy-carrying molecule similar in structure to nucleotides. Example: ATP has three phosphate groups.
Exam Tips
Key Definitions to Remember
- Nucleotide: Building block of DNA and RNA.
- Antiparallel Strands: DNA strands running in opposite directions.
- Complementary Base Pairing: Specific pairing of bases in DNA.
Common Confusions
- Confusing the bases in DNA and RNA (Thymine vs. Uracil).
- Misunderstanding the directionality of DNA strands (5' to 3').
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 do DNA strands pair? Through complementary base pairing: A with T, and G with C.
- What is semi-conservative replication? Each new DNA molecule conserves one original strand.
What Examiners Usually Test
- Understanding of nucleotide structure and function.
- Ability to explain DNA replication and base pairing.