Which of the following traits lead to cystic fibrosis?

Appeared in: HP CHO -9 October 2022

Explanation

Cystic Fibrosis (CF) is a classic example of an autosomal recessive genetic disorder.
This inheritance pattern means an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease.
The mutation occurs in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, which is located on chromosome 7, an autosome (non-sex chromosome).
Individuals with only one copy of the mutated gene are carriers and are typically asymptomatic but can pass the gene to their offspring.

Option A: This pattern requires only one copy of the mutated gene to cause disease, and it typically appears in every generation. CF requires two copies and can skip generations.
Option C: This involves a mutation on the X chromosome. The gene for cystic fibrosis (CFTR) is located on chromosome 7, which is an autosome, not a sex chromosome.
Option D: This involves a mutation on the X chromosome and primarily affects males. The gene for cystic fibrosis is on an autosome, affecting males and females equally.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Genetic inheritance pattern of Cystic Fibrosis as background academic context rather than a clinical decision trigger.
Understanding the autosomal recessive pattern is crucial for providing accurate genetic counseling to families with a history of CF.
Carrier screening is often recommended for couples planning a pregnancy, especially in populations with a higher incidence of CF, to assess their risk of having an affected child.
The diagnosis of CF is often confirmed by a sweat chloride test, as the defective CFTR protein leads to abnormally high levels of chloride in the sweat.

How to Approach the Question

First, identify the core question: it asks for the specific mode of genetic inheritance for cystic fibrosis.
This is a factual recall question. Access your knowledge of common Mendelian disorders and their inheritance patterns.
Analyze the options. Differentiate between 'autosomal' (gene on a non-sex chromosome) and 'X-linked' (gene on the X chromosome), and between 'dominant' (one gene copy needed for expression) and 'recessive' (two gene copies needed).
Recall that cystic fibrosis affects males and females equally and can 'skip' a generation (i.e., unaffected parents can have an affected child). These are the classic hallmarks of an autosomal recessive disorder.
Select the option that matches this pattern and eliminate the others based on the definitions of dominant and X-linked inheritance.

Concept Tested & Keywords

QrARbfBUKGtgtP3TWjFYRt

E6 Medicine Harrison 22e Part 2 p. 1695-1697

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

Practise the full HP CHO -9 October 2022

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