Example for autosomal recessive inheritance

ESIC Nursing Officer - 2019 (Shift-2)

Pathology & Genetics

Easy

Appeared in: ESIC Nursing Officer - 2019 (Shift-2)

Explanation

Cystic fibrosis is a well-known metabolic disorder that follows an autosomal recessive inheritance pattern.
This means an individual must inherit two copies of the non-working CFTR gene, one from each parent, to have the disease.
Parents of an affected child are typically obligate carriers, meaning they each have one copy of the mutated gene but do not show symptoms of the disease.
The recurrence risk for carrier parents to have another affected child is 25% with each pregnancy.

Option A: Hemophilia is a bleeding disorder that follows an X-linked recessive inheritance pattern, not autosomal recessive.
Option C: This is a broad, heterogeneous category of disorders, not a single disease with one mode of inheritance. It includes conditions with various genetic patterns (dominant, recessive, chromosomal).
Option D: Similar to craniofacial disorders, this is a wide-ranging category. Many skeletal disorders are autosomal dominant (e.g., Achondroplasia, Marfan syndrome), while others can be recessive or X-linked.

Visual 1: Punnett Square Diagram - A 2x2 grid illustrating the 25% chance of an 'aa' (affected) offspring, 50% chance of 'Aa' (carrier), and 25% chance of 'AA' (unaffected) from two 'Aa' carrier parents. This visually clarifies the risk ratios in autosomal recessive inheritance.
Visual 2: Pedigree Chart - A chart showing an autosomal recessive pattern, characterized by the disorder skipping generations and appearing in siblings of both sexes, with parents who are unaffected carriers.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Modes of Genetic Inheritance (Autosomal Recessive) as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in genetic counseling, helping families understand inheritance patterns, carrier status, and risks for future pregnancies.
For a condition like Cystic Fibrosis, nursing care involves managing symptoms (respiratory therapy, pancreatic enzyme replacement), patient education, and supporting the family.
What if? If a patient has Hemophilia, the nursing focus shifts to bleeding precautions, administration of clotting factors, and counseling about its X-linked inheritance, which has different implications for male and female relatives.

How to Approach the Question

First, define the key term in the question: 'autosomal recessive inheritance'. This means it's not on a sex chromosome ('autosomal') and requires two copies of the gene to manifest ('recessive').
Evaluate each option against this definition.
Recall or deduce the inheritance pattern of Hemophilia. It's a famous example of X-linked inheritance, so it can be eliminated.
Recognize that 'Craniofacial disorders' and 'Skeletal disorders' are broad categories, not specific diseases. In genetics questions, such general terms are often distractors because they contain diseases with many different inheritance patterns.
Identify Cystic fibrosis as a classic, specific example of an autosomal recessive disease taught in nursing curricula.
Confirming that Cystic fibrosis fits the definition and the other options do not leads to the correct answer.

Concept Tested & Keywords

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