[sevlex]

“but also single X, XXY, XYY and XXXY”
~~~~~~~~~~~~~

A single X would be an unfertilized egg - a hsploid.

The presence of a Y makes a male.

This woke guy is an idiot.

[I-ambush]

Single X, or XO, results in Turner’s syndrome. Female genitalia with webbed neck and infertility due to “stream ovaries.”

[IndispensableDestiny]

A single X would be an unfertilized egg - a hsploid.

A single X is a female with Turner syndrome.

Here are the others. The leading number is the total number of chromosomes instead of the typical 46.

Trisomies:
47,XXY (Klinefelter syndrome)
47,XXX (Trisomy X)

Tetrasomies:
48,XXYY
48,XXXY
48,XXXX

Pentasomies:
49,XXXXY
49,XXXXX

[stremba]

Single X humans actually do exist. It’s a condition called Turners Syndrome. It’s rare, and those with it are female, but usually non-fertile.