sex chromosome 
noun
A chromosome concerned in determining the sex of an organism, typically one of two kinds.The abnormal behavior of an unidentified sex chromosome has also been reported in D. subobscura....
- The Y chromosome is the male-specific sex chromosome that is passed from father to son in the same way that surnames are passed from father to son.
- It is genetic, but not linked to a sex chromosome like hemophilia, so either parent can pass porphyria on to any child.
In humans and other mammals females have two similar sex chromosomes (XX) while males have dissimilar ones (XY). In birds and some other animals, females have dissimilar sex chromosomes (ZW) and males similar ones (WW). Some other organisms have a sex chromosome present only in one sex.