Exercise Solutions Available
Step-by-step answers for all textbook questions in this chapter
Quick Summary
Molecular genetics explains how hereditary information is stored, copied, and expressed. The main flow to master is DNA replication -> transcription -> translation.
DNA Structure
- Double helix
- Two antiparallel polynucleotide strands
- Sugar-phosphate backbone
- Complementary base pairing: A-T and G-C
DNA vs RNA
| DNA | RNA |
|---|---|
| Deoxyribose sugar | Ribose sugar |
| Thymine present | Uracil present |
| Usually double stranded | Usually single stranded |
| Stores genetic information | Helps express genetic information |
DNA Replication
Main ideas:
- Semi-conservative
- Complementary base pairing
- New strands are synthesised using old strands as templates
Transcription
DNA information is copied into RNA.
Key points:
- Uses one DNA strand as template
- Produces RNA transcript
- In eukaryotes, primary transcript may undergo processing
Translation
mRNA codons are read at ribosomes to build a polypeptide.
Important participants:
- mRNA
- tRNA
- ribosome
- amino acids
Genetic Code
- Triplet
- Degenerate
- Nearly universal
- Has initiation and termination signals
Important Questions
One Mark
1. What is the central dogma? 2. Name the base present in RNA instead of thymine. 3. What is a codon?
Short Answer
1. Distinguish between DNA and RNA. 2. Explain the features of genetic code. 3. Write the steps involved in transcription.
Long Answer
1. Explain the structure of DNA. 2. Explain DNA replication. 3. Explain transcription and translation.
Common Mistakes
- Reversing thymine and uracil.
- Treating replication and transcription as the same process.
- Forgetting the role of tRNA in translation.
- Writing central dogma without direction.
Revision Checklist
- [ ] DNA structure
- [ ] DNA vs RNA table
- [ ] Replication sequence
- [ ] Transcription and translation
- [ ] Features of genetic code
Frequently Asked Questions
The central dogma describes information flow from DNA to RNA to protein.