Case Study 1: Gene Mutation and Sickle Cell Anaemia
Sickle cell anaemia is a genetic disorder caused by a change in a single
nucleotide of the β-globin gene. This mutation alters haemoglobin structure,
producing sickle-shaped RBCs under low oxygen conditions.
1. The type of mutation responsible is
A. Frameshift mutation
B. Point mutation
C. Chromosomal deletion
D. Polyploidy
✅ Answer: B
📘 Explanation: A single base substitution causes the disorder.
2. Which amino acid substitution occurs?
A. Glycine → Alanine
B. Valine → Glutamic acid
C. Glutamic acid → Valine
D. Alanine → Glycine
✅ Answer: C
📘 Explanation: Valine replaces glutamic acid at 6th position.
3. Why does haemoglobin structure change?
A. Due to deletion of gene
B. Due to frameshift mutation
C. Due to altered amino acid sequence
D. Due to chromosome duplication
✅ Answer: C
📘 Explanation: Single amino acid change alters protein folding.
Case Study 2: Frameshift Mutation
Insertion or deletion of bases alters the reading frame, producing a
completely different protein.
4. Which mutation results in frameshift?
A. Substitution
B. Duplication
C. Insertion
D. Inversion
✅ Answer: C
📘 Explanation: Insertion changes codon reading frame.
5. Frameshift mutation is severe because
A. Affects one amino acid
B. Stops transcription
C. Changes downstream codons
D. Increases gene dosage
✅ Answer: C
📘 Explanation: Entire protein sequence is altered.
Case Study 3: Chromosomal Mutations
6. Loss of chromosome segment is called
A. Duplication
B. Deletion
C. Inversion
D. Translocation
✅ Answer: B
7. Exchange between non-homologous chromosomes
A. Inversion
B. Deletion
C. Duplication
D. Translocation
✅ Answer: D
8. Which mutation increases gene dosage?
A. Deletion
B. Duplication
C. Inversion
D. Translocation
✅ Answer: B
Case Study 4: Genome Mutations
9. Down syndrome is caused due to
A. Monosomy
B. Trisomy 21
C. Polyploidy
D. Frameshift mutation
✅ Answer: B
10. Which process causes aneuploidy?
A. Crossing over
B. Fertilisation
C. Nondisjunction
D. Mutation repair
✅ Answer: C
11. Turner syndrome constitution
A. XX
B. XY
C. XO
D. XXY
✅ Answer: C
Case Study 5: Mutagens
12. UV radiation forms
A. Frameshift
B. Thymine dimers
C. Stop codons
D. Duplication
✅ Answer: B
13. Nitrous acid causes
A. Deleting bases
B. Deamination
C. Blocking replication
D. Increasing chromosomes
✅ Answer: B
14. Viruses cause mutations by
A. Crossing over
B. DNA repair
C. Transposition
D. Transcription
✅ Answer: C
Case Study 6: Somatic and Germinal Mutations
15. Which mutation contributes to evolution?
A. Somatic
B. Silent
C. Germinal
D. Neutral
✅ Answer: C
📘 Explanation: Germ cell mutations are inherited.
16. Cancer is generally caused due to
A. Germinal mutations
B. Neutral mutations
C. Silent mutations
D. Somatic mutations
✅ Answer: D