Mutations that change protein structure
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Flip to reveal answersWhat type of mutation causes sickle-cell anaemia?
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All 12 Flashcards — Mutations that change protein structure
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Question
What type of mutation causes sickle-cell anaemia?
Answer
A **base substitution** — one base in the haemoglobin gene is swapped for another.
Question
Which protein is affected in sickle-cell anaemia?
Answer
**Haemoglobin** — the oxygen-carrying protein in red blood cells.
Question
Which amino acid change does the sickle-cell mutation cause?
Answer
**Glutamic acid is replaced by valine** in the haemoglobin chain.
Question
How many bases and amino acids actually change?
Answer
Just **one base** in the gene, which changes just **one amino acid** in the protein.
Question
What is HbS?
Answer
**Sickle haemoglobin** — the abnormal haemoglobin made by the sickle-cell allele. It sticks together into fibres when oxygen is low.
Question
Why do red blood cells become sickle-shaped?
Answer
When oxygen is low, abnormal haemoglobin (HbS) **sticks together into fibres** that pull the cell into a rigid sickle (crescent) shape.
Question
Define a base substitution.
Answer
A mutation in which **one base in the DNA is replaced by a different base**.
Question
Define phenotype.
Answer
The **observable characteristics** of an organism — here, the symptoms of sickle-cell anaemia.
Question
Why do sickled cells cause pain?
Answer
They are **rigid** and get stuck, **blocking small blood vessels (capillaries)**.
Question
Why does sickle-cell anaemia cause tiredness and anaemia?
Answer
Sickled cells **carry less oxygen** and are **destroyed faster**, so tissues get less oxygen and there are too few red blood cells.
Question
State the cascade from mutation to phenotype in order.
Answer
Base substitution -> changed codon -> one amino acid changed (glutamic acid -> valine) -> abnormal haemoglobin -> sickled cells -> sickle-cell anaemia.
Question
Why can one base change cause a serious disease?
Answer
The gene is a **code**: one base change can change one codon, then one amino acid, then the **shape and behaviour** of the whole protein.
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Topic 4.2 hub
Protein synthesis
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