Hetero chromosomes, also known as sex chromosomes, refer to the chromosomes that determine the biological sex of an individual. In humans, these are typically labeled as X and Y chromosomes, with females having two X chromosomes and males having one X and one Y chromosome. Other terms that can be used as synonyms for hetero chromosomes include sex chromosomes, allosomes, or gonosomes. Allosomes refer to a pair of chromosomes that differ in males and females, while gonosomes refer to sex chromosomes that determine the sex of an individual. Regardless of the term used, hetero chromosomes play a crucial role in determining the physical and biological traits of individuals.