If an autosome is present in only one copy at conception, that individual will not develop to term. Yet human males have only one copy of the X chromosome and they do develop normally. Why is there a difference?
Workings of an autosome and an x chromosome are completely different.
An autosome requires two copies so as to maintain the chromosome number in the human species where one is from the father and other from the mother.
While the x chromosome is a type of sex chromosome which determines our sex. The x chromosome encodes feminine characters while the y encodes masculine characters.
It only changes the body by a little bit and so a single copy is enough.The basic anatomy and morphology of a male and female is more or less same with subtle changes such as broader hips of women and the hoarse voice of men.While the autosomes determine other important features such as blood group type immunity, eye colour etc.Thus two copies of it are required