Preparatory Mindset
The central dogma (DNA → RNA → Protein) is the single most important concept in molecular genetics. Everything else builds on this. Understand how each step works and where regulation occurs.
Core Concepts
- Central dogma: DNA is transcribed to RNA, RNA is translated to Protein
- Gene structure: Promoter (5', binds RNA polymerase), Exons (coding), Introns (non-coding, spliced out), UTRs (untranslated regions)
- Types of RNA: mRNA (messenger — carries code), tRNA (transporter — brings amino acids), rRNA (ribosomal — catalytic)
- RNA processing: 5' cap added, introns spliced out, poly-A tail added at 3' end
- Alternative splicing: One gene can produce multiple different proteins by varying exon combinations
- Translation initiation: Always starts at AUG codon (methionine)
- CpG islands: CG-rich regions in promoters; methylation → gene silencing (epigenetic regulation)
- Pseudogenes: DNA sequences that resemble functional genes but have mutations preventing expression
- Promoter: Located in 5' region; binds RNA polymerase and transcription factors
- Poly-A signal: Located in 3' region; signals addition of poly-A tail
High-Yield Points
- Central dogma: DNA → RNA → Protein (unidirectional in cells)
- Alternative splicing explains how 20,000 genes produce >100,000 proteins
- CpG island methylation = gene silencing (epigenetics)
- mRNA: coding; tRNA: amino acid delivery; rRNA: ribosome component
Topic Summary
Genes are transcribed to pre-mRNA, processed (capped, spliced, poly-A tailed), then translated to protein. Alternative splicing and epigenetic regulation add complexity beyond the DNA sequence.