Trisomy of chromosome no. 21 causes?

AIIMS Raipur NO - 2019 (Shift-2)

Pathology & Genetics

Easy

Appeared in: AIIMS Raipur NO - 2019 (Shift-2)

Explanation

Down's syndrome is caused by a chromosomal abnormality known as Trisomy 21.
This means that individuals with Down's syndrome have three copies of chromosome 21 in their cells, instead of the usual two.
The image provided is a karyotype that visually confirms the presence of three chromosome 21s, which is diagnostic for Down's syndrome.
It is the most common nonlethal trisomy and is associated with distinct physical features, intellectual disability, and various health issues like congenital heart defects.

Option B: Turner's syndrome is caused by a monosomy, not a trisomy. It results from having only one X chromosome (45,X0) instead of two.
Option C: Edward syndrome is caused by Trisomy 18, which is the presence of an extra copy of chromosome 18.
Option D: Klinefelter syndrome is a sex chromosome disorder in males caused by the presence of an extra X chromosome (47,XXY).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The question tests the knowledge of the specific chromosomal abnormality that causes Down's syndrome as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in supporting families of children with Down's syndrome, providing education on developmental expectations, managing associated health problems (like cardiac or gastrointestinal issues), and connecting them with support services.
Prenatal screening and diagnostic tests (like amniocentesis or chorionic villus sampling to obtain a karyotype) are offered during pregnancy to detect chromosomal abnormalities. Nurses must be able to explain these tests to expectant parents.
What if? If the karyotype showed three copies of chromosome 18 instead of 21, the diagnosis would be Edward syndrome, which has a much more severe prognosis and different clinical management priorities, often focusing on palliative care due to its high lethality.

How to Approach the Question

First, identify the core of the question: it's asking for the specific condition linked to 'Trisomy of chromosome no. 21'.
Analyze the image provided. It's a karyotype, a map of chromosomes. Locate chromosome 21 and count the number of copies. You will see three, which confirms 'Trisomy 21'.
Recall or look up the definitions of the genetic conditions listed in the options.
Match the identified genetic abnormality (Trisomy 21) with the correct condition.
Down's syndrome is the condition caused by Trisomy 21.
Evaluate the other options to confirm they are incorrect: Turner's syndrome is Monosomy X, Edward syndrome is Trisomy 18, and Klinefelter syndrome is XXY.

Concept Tested & Keywords

Concept Tested: The question tests the knowledge of the specific chromosomal abnormality that causes Down's syndrome.
Stem keywords: Trisomy, chromosome no. 21
Lead-in keywords: causes

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