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Each cell of a human body contains 46 chromosomes. So every cell must contain a pair of sex-chromosome. Is it true? Then a cell of a male and a cell of a female are always different and never be the same?

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Like the other answer already said: yes, all cells in the human body contain all 2x 23 chromosomes (with the exception of cells that loose all nuclear DNA during maturation, like red blood cells, or cell produces by meiosis, which contain only a single set of 1x 23 chromosomes).

However, the more interesting part of your question remains to be answered:

Then a cell of a male and a cell of a female are always different and never be the same?

Technically it is true, that cells from a male and female can never be the same, however that difference is vanishingly small.

Genetically the difference is that female cells have two X chromosomes and male cells have one X and one Y. However:

  • in all female cells one of the two X chromosomes is permanently silenced (turned off), so essentially they also have only one (active) X chromosome.
  • the male exclusive Y chromosome is tiny. Size wise it is ~1% of the human genome, but it only has ~200 genes (of which only a portion is protein coding), which is even below 1% of all human genes (there are ~25.000 protein coding genes, around twice that much in total). Many of these genes are also only used/active in male exclusive organs.

These two points taken together mean that the majority of male and female cells do actually have the same active genes - and are therefore "the same" (there are of course many many other factors in biology, including individual differences, that require putting this into quotes).

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    $\begingroup$ +1 for recognizing that red blood cells are not the only cells that extrude their nucleus on maturation $\endgroup$
    – De Novo
    Feb 19, 2019 at 14:19
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All cells except mature rbcs contain genetic material. So every cell must contain 46 chromosome containing sex chromosome as well

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    $\begingroup$ Please provide a citation or link in reference to support for your answer. Thanks. $\endgroup$
    – theforestecologist ♦
    Feb 18, 2019 at 20:56
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Yes, all cells except mature RBC have all the 23 pairs(22 autosomes + XX/XY) but due to different regulation mechanisms and deactivation due to heterochromatin, only the part of DNA actually useful to that particular cell type (like the gene for insulin in beta cells of pancreas) is used by it.

For Example: In the testis in the Leydig cells, only the androgen producing genes and other related genes are kept active.

https://en.wikipedia.org/wiki/Heterochromatin#Function https://en.wikipedia.org/wiki/Regulation_of_gene_expression

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    $\begingroup$ Please provide a citation or link in reference to support for your answer. Thanks. $\endgroup$
    – theforestecologist ♦
    Feb 18, 2019 at 20:48

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