The number of sex chromosomes in a human kidney cell is

Concept: In a diploid human somatic cell, chromosomes occur in homologous pairs. One member of each pair is inherited from each parent.

The 46 chromosomes comprise 22 pairs of autosomes and one pair of sex chromosomes.

Application: A kidney cell is an ordinary somatic cell. Therefore, its diploid chromosome complement contains two sex chromosomes, which form one pair.

Contrast:

• One pair means two sex chromosomes, which is the ordinary diploid count.

• Two pairs would mean four sex chromosomes in one kidney cell.

• Three pairs would mean six sex chromosomes in one kidney cell.

• More than one of the above would require multiple different pair counts to describe the same ordinary kidney-cell karyotype.

• None of the above would require the standard diploid count to be absent from the listed numerical choices.

Cross-check: The standard human karyotype count gives 44 autosomes plus 2 sex chromosomes, totaling 46 chromosomes. Thus, the sex chromosomes form one pair.

Result: one pair.