Which of the following is an X-linked recessive disease?

Appeared in: DSSSB - 29 August 2019 (Shift-2)

Explanation

Colour blindness is a classic example of an X-linked recessive disorder.
The gene responsible for this condition is located on the X chromosome.
Males are more commonly affected because they have only one X chromosome (XY). If their single X chromosome carries the recessive gene, they will express the trait.
Females (XX) need to inherit the faulty gene on both of their X chromosomes to be affected, making them more likely to be carriers than to have the condition.

Option B: Huntington's disease is an autosomal dominant disorder, not X-linked recessive.
Option C: Achondroplasia, a form of dwarfism, is an autosomal dominant disorder.
Option D: Polycystic kidney disease is most commonly an autosomal dominant disorder (ADPKD). A rarer autosomal recessive form (ARPKD) exists, but it is not X-linked.

Clinical Relevance

Nursing practice connection: Knowing Genetic Inheritance Patterns helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding genetic inheritance patterns is crucial for nurses to provide accurate patient education and genetic counseling, especially regarding family planning and risk assessment for future offspring.
Nurses can help families construct a pedigree (family health history) to identify patterns of disease, which can guide diagnostic testing and management.
What if? If a female patient is a known carrier for an X-linked recessive disorder like Hemophilia or Duchenne muscular dystrophy, the nurse must counsel her that there is a 50% chance with each male pregnancy that the son will be affected.

How to Approach the Question

First, identify the key concept in the question, which is 'X-linked recessive disease'.
Recall the definition of X-linked recessive inheritance: the gene is on the X chromosome, and it predominantly affects males.
Systematically evaluate each option based on your knowledge of genetic disorders.
Eliminate options with different inheritance patterns. Huntington's, Achondroplasia, and Polycystic Kidney Disease are primarily autosomal dominant.
Confirm that Colour blindness fits the criteria for an X-linked recessive condition.
Select the option that correctly matches the inheritance pattern asked in the question.

Concept Tested & Keywords

QO98S9yhDz5Y7d1UkL5vsY

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 153-155

E6 Pathology-Vandana Puri & Kavita Gaur Textbook of Pathology and Genetics p. 487-489

E6 Medicine Davidson Principles Practice 24e p. 67-69

Practise the full DSSSB - 29 August 2019 (Shift-2)

Attempt every question from this paper in a timed mock, then review the full solution for each one.