Protein synthesis: The Most Important Concept in HSC Biology (No One Gets Right)

Which came first — DNA or proteins? 🧬🥚🐔
In this video, I’ll break down exactly how DNA makes proteins through transcription and translation, with clear visuals, analogies (donut vs banana 🍩🍌 anyone?), and common mistakes you NEED to avoid if you want a Band 6 in HSC Biology.

By the end, you’ll also understand how a tiny mutation can cause a devastating disease like Sickle Cell Anaemia (and why CRISPR might soon fix it).
📝 Test yourself:
Here are two protein synthesis questions to practise 👇

Question 1 (Easy)
Describe the process of translation and explain how the structure of tRNA allows it to perform its role. (3 marks)

Sample answer:
Translation occurs at the ribosome where the mRNA sequence is read in codons. tRNA molecules, which have an anticodon at one end and an amino acid at the other, temporarily bind to complementary mRNA codons. This allows the ribosome to catalyse peptide bond formation between amino acids, producing a polypeptide chain.

Marking criteria:
Identifies the location and purpose of translation (1 mark)
Describes the role of tRNA and anticodon-codon binding (1 mark)
Explains peptide bond formation and polypeptide synthesis (1 mark)

Question 2 (Hard)
Using an example, explain how a mutation in a gene can lead to the symptoms of a named genetic disease. (4 marks)

Sample answer:
A point mutation changes one base in the haemoglobin gene (GAG to GTG), resulting in the substitution of glutamic acid with valine in the polypeptide chain. This alters the haemoglobin’s structure, causing it to polymerise under low oxygen conditions. The red blood cells become sickle-shaped, reducing oxygen-carrying capacity and leading to symptoms like anaemia, pain, and blocked blood vessels.

Marking criteria:
Identifies the point mutation and amino acid substitution (1 mark)
Explains how haemoglobin structure changes (1 mark)
Links sickle shape to reduced oxygen transport (1 mark)
Describes resulting symptoms (1 mark)

✅ BONUS:
At the end, I reveal the answer to the ultimate question — which came first? (Hint: it’s actually RNA…)

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#biology #hscbiology #proteinsynthesis #transcription #translation #sicklecell #ATAR99