Which chromosomal abnormality is most commonly associated with Down syndrome in prenatal diagnosis?

Appeared in: NCL (Northern Coalfields Limited)-NO

Explanation

Down syndrome is the most common nonlethal trisomy, resulting from an extra copy of chromosome 21.
This condition is referred to as Trisomy 21.
Approximately 95% of Down syndrome cases are due to Trisomy 21, where every cell in the body has three copies of chromosome 21 instead of the usual two.
The risk of having a child with Trisomy 21 increases with maternal age.

Option A: Monosomy X is the absence of one of the two X chromosomes in females.
Option C: Trisomy 13 involves an extra copy of chromosome 13.
Option D: Trisomy 18 involves an extra copy of chromosome 18.

Visual 1: Karyotype - A human karyotype illustrating Trisomy 21, clearly showing three copies of chromosome 21 instead of the usual pair. This visual helps learners directly see the genetic basis of Down syndrome.
Visual 2: Infographic - A comparative chart showing the key physical features associated with Down syndrome, Edwards syndrome, and Patau syndrome to help differentiate between the common trisomies.

Clinical Relevance

Nursing practice connection: Use the key finding related to Chromosomal Abnormalities and Associated Syndromes to guide bedside assessment, documentation, and the next nursing action.
Nurses play a crucial role in educating and supporting families during prenatal screening and diagnosis for chromosomal abnormalities.
Understanding the genetic basis of conditions like Down syndrome is essential for providing accurate information and compassionate counseling to expectant parents.
Knowledge of the increased risk associated with advanced maternal age allows nurses to identify patients who may benefit from more detailed screening discussions.

How to Approach the Question

This is a factual recall question that tests your knowledge of common genetic disorders.
First, identify the key term in the question: 'Down syndrome'.
Recall the specific chromosomal abnormality associated with Down syndrome. The name itself is a clue, as it is often called Trisomy 21.
Scan the options to find the one that matches your knowledge. 'Trisomy 21' is listed as an option.
Eliminate the other options by recalling the syndromes they are associated with (Monosomy X with Turner, Trisomy 13 with Patau, Trisomy 18 with Edwards).

Concept Tested & Keywords

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Practise the full NCL (Northern Coalfields Limited)-NO

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