Molecules (Continuity and change)
- DNA replication
- Exact copies of DNA
- Reproduction
- Growth
- Tissue replacement
- Semi-conservative
- One old, one new strand
- Complementary base pairing
- High accuracy
- Enzymes
- Helicase: breaks hydrogen bonds
- DNA polymerase: builds strand
- PCR
- 95 °C denature
- 55 °C primers anneal
- 72 °C Taq extends
- Doubles each cycle
- Gel electrophoresis
- DNA negative
- Moves to positive electrode
- Small fragments travel further
- DNA profiling
- STR lengths
- Paternity
- Forensics
- More markers, fewer false matches
- Leading and lagging strands HL only
- 5' to 3' only
- Continuous vs discontinuous
- Okazaki fragments
- Prokaryotic enzymes HL only
- Primase: RNA primers
- Pol III: extends, proofreads
- Pol I: replaces primers
- Ligase: seals gaps
- Exact copies of DNA
- Protein synthesis
- Transcription
- RNA polymerase
- Template strand
- A pairs with U
- DNA unchanged
- Gene expression
- Not all genes expressed
- Switched on or off
- Translation
- mRNA on small subunit
- Two tRNAs on large subunit
- Codon–anticodon pairing
- Peptide bonds
- Genetic code
- Triplet: 64 codons
- Degenerate
- Universal
- AUG start, 3 stops
- Point mutation
- Sickle cell: GAG to GUG
- Glu to Val
- Haemoglobin S fibres
- Promoter and directionality HL only
- Transcription factors bind
- 5' to 3' synthesis
- mRNA processing HL only
- Introns removed
- 5' cap, polyA tail
- Alternative splicing
- Initiation and modification HL only
- A, P, E sites
- Pre-proinsulin to insulin
- Proteasomes recycle amino acids
- Transcription
- Mutation and gene editing
- Types of gene mutation
- Substitution
- Insertion
- Deletion
- Consequences
- SNPs
- Degeneracy may hide change
- Frameshift
- Causes
- Chemical mutagens
- UV, X-rays, gamma
- Replication or repair errors
- Randomness
- Anywhere in genome
- No deliberate changes
- Germ vs somatic
- Germ: inherited
- Somatic: cancer
- Source of variation
- Only source of new alleles
- Essential for natural selection
- Gene knockout HL only
- Make gene inoperative
- Knockout libraries
- CRISPR–Cas9 HL only
- Guide RNA targets
- Cas9 cuts
- Sickle-cell therapy
- Ethics and regulation
- Conserved sequences HL only
- Functional requirements
- Slower mutation rates
- Types of gene mutation