Genetic disorder, Down syndrome is caused by defect in chromosome number?

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

Explanation

Down syndrome, also known as Trisomy 21, is a genetic condition caused by the presence of an extra, third copy of chromosome 21.
It is the most common chromosomal disorder, occurring in approximately 1 in 700 live births.
The extra genetic material leads to characteristic physical features (e.g., flat facial profile, single palmar crease), developmental delays, and intellectual disability.
Individuals with Down syndrome also have an increased risk for certain health issues, including congenital heart defects and leukemia.

Option B: An extra copy of chromosome 18 causes Edwards syndrome, not Down syndrome.
Option C: An extra copy of chromosome 13 is the cause of Patau syndrome.
Option D: While abnormalities of chromosome 22 exist, a full trisomy is rare and usually not compatible with life. A more common disorder is DiGeorge syndrome, which is caused by a deletion on chromosome 22 (22q11.2), not an extra chromosome.

Clinical Relevance

Nursing practice connection: Knowing Chromosomal abnormalities and associated genetic disorders helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses are central to educating and supporting families with a new diagnosis of Down syndrome, covering topics from feeding techniques for infants with low muscle tone to navigating early intervention services.
A crucial nursing role involves discussing prenatal screening options (like NIPT) and diagnostic tests (like amniocentesis) with expectant parents, explaining the risks, benefits, and what the results might mean.
What if? If a newborn presents with features of Trisomy 18 (Edwards syndrome) instead, the nursing priority shifts from developmental support to compassionate, palliative-focused care, as survival beyond the first year is rare.

How to Approach the Question

This is a direct recall question linking a specific genetic disorder to its chromosomal cause.
First, identify the key terms in the question: 'Down syndrome' and 'chromosome number'.
Access your memory for the common autosomal trisomies. The three most frequently tested are Trisomy 13, 18, and 21.
Directly associate 'Down syndrome' with 'Trisomy 21'. This is a foundational piece of genetic knowledge.
Eliminate the other options by recalling that Trisomy 18 is Edwards syndrome and Trisomy 13 is Patau syndrome.

Concept Tested & Keywords

QII_LyNLA4AbC6moylNx_G

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed pp. 176-178, 173-175

E6 Text Book Of Pediatric Nursing 3rd Panchali Pal — Part 3 (pp 477-702 of 713) p. 93-95

Practise the full RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

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