Which is a genetic disorder of girls caused by a missing or defective X chromosome?

Appeared in: DSSSB October 2024

Explanation

Turner syndrome is a genetic condition that affects only females.
It is caused by a chromosomal abnormality where one of the X chromosomes is completely or partially missing (monosomy X).
The typical karyotype is 45,X instead of the normal female 46,XX.
Key clinical features include short stature, failure of the ovaries to develop (gonadal dysgenesis), and a webbed neck.

Option A: Edward syndrome is caused by an extra copy of chromosome 18 (Trisomy 18), not a missing X chromosome. It affects both males and females.
Option C: Down syndrome is caused by an extra copy of chromosome 21 (Trisomy 21). It is the most common autosomal trisomy and is not related to a missing sex chromosome.
Option D: Patau syndrome is caused by an extra copy of chromosome 13 (Trisomy 13). It is a severe trisomy and not a sex chromosome abnormality.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Genetic disorders related to chromosomal abnormalities as background academic context rather than a clinical decision trigger.
Early diagnosis of Turner syndrome through karyotyping is crucial for timely intervention, including growth hormone therapy to address short stature and estrogen therapy to induce puberty.
Nurses play a key role in providing long-term support and education to patients and families regarding the management of associated health issues like heart defects, kidney problems, and learning disabilities.
Genetic counseling is essential for families to understand the condition, its non-hereditary nature in most cases (due to a sporadic event during gamete formation), and management options.

How to Approach the Question

First, break down the question stem to identify the key criteria: 1) genetic disorder, 2) affects girls, and 3) caused by a missing or defective X chromosome.
The most specific clue is 'missing or defective X chromosome,' which points to a monosomy involving a sex chromosome.
Evaluate each option against these criteria.
Recall or deduce that Edward, Down, and Patau syndromes are trisomies (involving an extra chromosome) of autosomal chromosomes (18, 21, and 13, respectively), not a missing sex chromosome.
Identify Turner syndrome as the only option that is a monosomy (missing chromosome) and specifically involves the X chromosome, affecting females.
This process of elimination, based on the type of chromosomal error (monosomy vs. trisomy) and the chromosome involved (sex vs. autosome), leads to the correct answer.

Concept Tested & Keywords

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 814-816

E6 Text Book Of Pediatric Nursing 3rd Panchali Pal — Part 3 (pp 477-702 of 713) p. 94-96

Practise the full DSSSB October 2024

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