Among the following which one is a chromosomal abnormality with extra chromosome 21?

Appeared in: AIIMS Raipur lecturer 2021

Explanation

Down syndrome is the correct answer as it is defined by the presence of an extra copy of chromosome 21.
This condition is also known as Trisomy 21.
It is the most common chromosomal disorder, occurring in about 1 in 700 live births.
The extra genetic material from chromosome 21 leads to the characteristic physical and developmental features of the syndrome.

Option B: Edwards syndrome is caused by an extra copy of chromosome 18 (Trisomy 18), not chromosome 21.
Option C: Klinefelter syndrome is a sex chromosome disorder (47,XXY), involving an extra X chromosome in males, not an extra autosome.
Option D: Turner syndrome is a sex chromosome disorder (45,X) where a female is missing an X chromosome. It is a monosomy, not a trisomy.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Identification of chromosomal abnormalities, specifically autosomal trisomies as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in supporting families of children with Down syndrome, from providing initial education at diagnosis to coordinating care for associated health issues like cardiac defects and hearing loss.
Prenatal screening tests (e.g., noninvasive prenatal testing or NIPT) can detect an increased risk for Trisomy 21, allowing for genetic counseling and preparation.
What if the question asked about the most common chromosomal abnormality in spontaneously aborted fetuses? The answer would be Turner Syndrome (45,X), as the vast majority of these conceptions do not survive to term.

How to Approach the Question

First, identify the key phrase in the question: 'extra chromosome 21'. This is the central fact you need to match.
This is a factual recall question. You need to access your knowledge about the genetic basis of common syndromes.
Systematically review each option:
Down syndrome: Recall or look up its chromosomal basis. It is Trisomy 21.
Edwards syndrome: Recall or look up its basis. It is Trisomy 18.
Klinefelter syndrome: Recall or look up its basis. It is 47,XXY (a sex chromosome issue).

Concept Tested & Keywords

Concept Tested: Identification of chromosomal abnormalities, specifically autosomal trisomies.
Stem keywords: chromosomal abnormality, extra chromosome 21
Lead-in keywords: which one is
Negative lead-in flag: false

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E6 Kaplan Sadock's Synopsis of Psychiatry-2022 (pp 1-3768 of 3768) p. 330-332

E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 139-141

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 176-178

Practise the full AIIMS Raipur lecturer 2021

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