Q.56 A clotting disorder which is sex-linked disease –
1. Sickle cell anaemia
2. Thalessemia
3. Hemophilia
4. Albenism
Hemophilia is the classic sex-linked clotting disorder, inherited via X-chromosome mutations affecting factors VIII or IX. Sickle cell anemia, thalassemia, and albinism follow autosomal patterns.
Sex-Linked Inheritance Basics
Sex-linked traits reside on X/Y chromosomes; X-linked recessive disorders like hemophilia predominantly affect males (XY inherits single mutated X from carrier mother).
Autosomal disorders affect both sexes equally via chromosomes 1-22.
Hemophilia A/B cause prolonged bleeding due to deficient clotting factors.
Correct Answer: 3. Hemophilia
Hemophilia (A: F8 gene; B: F9 gene) mutations on X chromosome lead to factor deficiencies; males express fully, females usually carriers.
50% risk for sons of carriers; daughters obligatory carriers from affected fathers.
Option Breakdown
| Option | Inheritance Pattern | Explanation | Sex-Linked? |
|---|---|---|---|
| 1. Sickle cell anaemia | Autosomal recessive | HBB gene (chr 11); hemoglobin mutation causes RBC sickling. | No |
| 2. Thalassemia | Autosomal recessive | HBA/HBB genes (chr 11/16); globin chain defects. | No |
| 3. Hemophilia | X-linked recessive | F8/F9 on X chromosome; classic bleeding disorder. | Yes |
| 4. Albenism | Autosomal recessive | TYR/OCA2 genes (chr 11/15); melanin synthesis block. | No |
Clinical Impact
Hemophilia manifests as joint bleeds, hemartrosis; treated with factor replacement/gene therapy.
Autosomal options lack sex bias in prevalence.
