Sex chromosome<span>, </span><span>either of a pair of chromosomes that determine whether an individual is male or female. The </span>sex<span> chromosomes of human beings and other mammals are designated by scientists as </span>X<span> and </span>Y<span>. In humans the sex chromosomes </span>comprise<span> one pair of the total of 23 pairs of chromosomes. The other 22 pairs of chromosomes are called </span>autosomes. I<span>ndividuals having two X chromosomes (XX) are female; individuals having one X </span>chromosome<span> and one Y chromosome (XY) are male. The X chromosome resembles a large autosomal chromosome with a long and a short arm. </span>