How many normal chromosomes are there in a male?

Appeared in: MP CHO-2020

Explanation

Humans have a total of 46 chromosomes arranged in 23 pairs.
22 of these pairs are autosomes (totaling 44 chromosomes), which determine non-sex-related traits.
The 23rd pair consists of sex chromosomes, which determine biological sex.
A normal male has one X and one Y chromosome (XY).
Therefore, the correct representation is 44 autosomes + XY sex chromosomes, totaling 46 chromosomes.

Option B: This notation (46+XX) suggests a total of 48 chromosomes (46 autosomes + 2 sex chromosomes), which is an abnormal number. A normal female has 44 autosomes + XX, for a total of 46.
Option C: This notation (45+XY) suggests a total of 47 chromosomes (45 autosomes + 2 sex chromosomes). This is an abnormal condition known as a trisomy, where there is an extra autosome.
Option D: This notation (46+YY) suggests a total of 48 chromosomes. This genetic makeup is not viable in humans as at least one X chromosome is essential for life.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Human Karyotype and Sex Chromosomes as background academic context rather than a clinical decision trigger.
Understanding the normal human karyotype is fundamental for genetic counseling and prenatal diagnosis.
Karyotyping is a laboratory procedure used to visualize and analyze chromosomes, allowing for the detection of aneuploidies (abnormal number of chromosomes) like Down syndrome (Trisomy 21), Turner syndrome (45,X), and Klinefelter syndrome (47,XXY).
Nurses play a role in collecting samples for genetic testing, educating patients about these tests, and providing support to families affected by chromosomal abnormalities.

How to Approach the Question

First, recall the total number of chromosomes in a normal human cell, which is 46.
Next, remember how these chromosomes are categorized: autosomes (non-sex chromosomes) and sex chromosomes.
Identify the number of autosomes. There are 22 pairs, which equals 44 autosomes.
Identify the sex chromosomes for a male, which are one X and one Y (XY).
Combine the number of autosomes and the sex chromosomes: 44 + XY.
Evaluate the given options to find the one that matches this correct formula.

Concept Tested & Keywords

Concept Tested: Human Karyotype and Sex Chromosomes
Stem keywords: normal chromosomes, male
Lead-in keywords: How many
Clinical cues: Age/sex group narrows the expected diagnosis, intervention, or normal reference range.

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 805-807

Practise the full MP CHO-2020

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