The number of chromosomes in a normal human cell is?

Appeared in: RRB Staff Nurse Kolkata-2015

Explanation

Normal human somatic (body) cells are diploid, containing a total of 46 chromosomes.
These chromosomes are organized into 23 pairs: 22 pairs of autosomes and one pair of sex chromosomes (XX for females, XY for males).
This number was definitively established in 1956 by Tjio and Levan.
Reproductive cells (gametes) are haploid, containing half the number, which is 23 chromosomes.

Option B: 48 is not the correct chromosome number for humans. Some species, like the potato, have 48 chromosomes.
Option C: 50 is not a chromosome number typically associated with any common organism in this context and is incorrect for humans.
Option D: 52 is not the correct chromosome number for humans.

Visual 1: Diagram: A human karyotype showing the 23 pairs of chromosomes, clearly labeling the autosomes (1-22) and the sex chromosomes (XX or XY). This helps visualize the correct number and arrangement.
Visual 2: Infographic: A comparison of diploid (2n) and haploid (n) cells, illustrating how somatic cells have 46 chromosomes and gametes have 23.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Human Chromosome Number as background academic context rather than a clinical decision trigger.
Understanding the normal chromosome count of 46 is fundamental for identifying genetic disorders caused by aneuploidy (an abnormal number of chromosomes).
Karyotyping is a crucial diagnostic tool in prenatal screening and for individuals with suspected genetic syndromes. It allows clinicians to visualize and count the chromosomes to detect abnormalities like trisomies (e.g., Down syndrome) or monosomies (e.g., Turner syndrome).
What if? If a prenatal karyotype revealed 47 chromosomes with an extra chromosome 21, the nurse would prepare to counsel the parents about the diagnosis of Down Syndrome and the associated health and developmental considerations.

How to Approach the Question

This is a direct factual recall question from basic biology and genetics.
Identify the key terms in the question: 'normal human cell' and 'number of chromosomes'.
Recall the fundamental concept that human somatic cells are diploid.
Remember the specific diploid number for humans, which is a foundational piece of knowledge in life sciences.
Select the option that matches this known fact (46).

Concept Tested & Keywords

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Practise the full RRB Staff Nurse Kolkata-2015

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