📖 Notes
LESSON 06 OF 17
DNA to Protein, Start to Finish
DNA to Protein, Start to Finish
The central dogma, transcription and translation mechanics, mutation types, and a classic MDCAT case study — sickle cell disease.
Central Dogma
DNA → mRNA → Protein
The Central Dogma
REFERENCEDNA --(Transcription)--> mRNA --(Translation)--> Protein
3
Bases per codon
1
Start codon (AUG)
3
Stop codons (UAA/UAG/UGA)
80S
Ribosome that translates
Transcription
- Occurs in the nucleus, carried out by RNA polymerase
- Template strand is read 3'→5', producing mRNA 5'→3'
- mRNA contains uracil, not thymine
Translation
- Happens at 80S ribosomes
- tRNA carries amino acids to the ribosome
- A codon = 3 mRNA bases = 1 amino acid
- Start codon: AUG (methionine) Stop codons: UAA, UAG, UGA
Mutation Types
- Point mutation: a single base change
- Frameshift mutation: insertion or deletion of a base, shifting every codon downstream
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Case Study: Sickle Cell Disease
A single base substitution (GAG→GTG) in the beta-globin gene replaces glutamic acid with valine. This distorts red blood cells under low oxygen — and carriers have a heterozygote advantage against malaria, a classic MDCAT discussion point.