Final answer:
The sex chromosome number variations XXX, XXY, XYY, and XO correspond to triplo-X, Klinefelter syndrome, males with an extra Y chromosome typically exhibiting few symptoms, and Turner syndrome, respectively.
Step-by-step explanation:
The phenotypes associated with the sex chromosome number variations XXX, XXY, XYY, and XO are as follows:
- XXX - This phenotype is called triplo-X and individuals are phenotypically female, with developmental delays and reduced fertility.
- XXY - Known as Klinefelter syndrome, individuals are phenotypically male and may have small testes, enlarged breasts, and reduced body hair. Advanced cases can include up to five X chromosomes, with surplus X chromosomes being inactivated as Barr bodies.
- XYY - Males with an extra Y chromosome typically exhibit few symptoms and may be taller than average, with increased risk of learning problems and delayed speech and language skills.
- XO - This is known as Turner syndrome and affects phenotypically female individuals who may have a short stature, webbed neck, hearing and cardiac impairments, and sterility.
Errors in meiosis can cause these sex chromosome number variations leading to the described phenotypes and associated health issues.