A chromosome that carries sex-determining genes. All other chromosomes are called *autosomes
. Sex chromosomes are widespread in the animal kingdom, associated with the fact that most animals have separate sexes. However most plants are hermaphrodite and sex chromosomes are correspondingly rare in the plant kingdom, although they are found in dioecious plants. In some such plant species sex is determined by one pair of alleles. However in certain angiosperm genera (e.g. Silene, Cannabis) cytologically identifiable sex chromosomes are seen.