The correct answer is option 4: sex chromosomes. Allosomes, also known as sex chromosomes, are responsible for determining the sex of an individual. In humans, the two types of sex chromosomes are X and Y, where males have one X and one Y chromosome (XY) while females have two X chromosomes (XX).

Option 1: Cell organelles are structures inside cells that perform specific functions, such as the nucleus, mitochondria, and chloroplasts. This is not related to allosomes.

Option 2: Plant hormones are chemical signals that regulate growth and development in plants. This is not related to allosomes.

Option 3: Alleles are different forms of a gene that occupy the same position on a specific chromosome. While alleles can be found on sex chromosomes, allosomes refer specifically to the entire sex chromosomes themselves rather than just the alleles they carry.

Therefore, the correct answer is option 4: sex chromosomes.