Sex-linked genetic disorders are associated with defects in the sex chromosomes, particularly the Y chromosome (in males) and the X chromosome (both in males and females).

If the genetic disorder is linked to the Y chromosome, then all males that have a defective Y chromosome would exhibit the disorder. This is because males have only one Y chromosome, which would not be masked by a normal, homologous chromosome.

Similarly, if the genetic disorder is linked to the X chromosome, then all males that have a defective X chromosome would also exhibit the disorder due to the same reason – males have only one X chromosome, which would not be masked by a normal, homologous chromosome.

On the other hand, females have two X chromosomes. If the defect occurs in one of the X chromosomes, the female would not exhibit the disorder. This is because the effects of the defective X chromosome is masked by the other normal X chromosome.

Females would only exhibit an X-linked genetic disorder if both of their X chromosomes are defective. On the other hand, males with a defective X chromosome would always exhibit the disorder, which is the reason why sex-linked disorders are more common in males.

**Nondisjunction** occurs when homologous chromosomes fail to separate during meiosis. This results in the formation of gametes with either too many or missing chromosomes.

In either case, the gametes would have an abnormal number of chromosomes. When these defective gametes form a zygote, the resulting offspring would exhibit genetic disorders.

One example of a genetic disorder that results from nondisjunction is Down syndrome. This genetic disorder is caused by three copies of chromosome 21, which is known as *Trisomy 21*.

Sex-linked disorders include colorblindness, which is the difficulty in distinguishing certain colors; hemophilia, which is a blood clotting disorder; and Duchenne muscular dystrophy, which results in the weakening of skeletal muscles.

Disorders of the sex chromosomes include Klinefelter’s syndrome and Turner’s syndrome. Klinefelter’s syndrome is a disorder in which males carry an extra X chromosome. Instead of the normal XY chromosome, they have at least two X chromosomes and at least one Y chromosome (XXY). The cause of this syndrome is the nondisjunction that occurs during meiosis I or II. This syndrome is characterized by having an appearance of a more feminine body structure and infertility in males. On the other hand, Turner’s syndrome occurs when there is an absence of the X chromosome. This is usually caused by an error in either the father’s sperm cell or in the mother’s egg cell. Turner syndrome affects the female and their development, which is why their organs are not fully developed and causing them to become sterile.

A sex-linked disorder is a disease or abnormality caused by some problem with the genes in the sex chromosomes.

Sex chromosome disorder is a disease or abnormality caused by extra or missing sex chromosome material (whole chromosomes or chromosome segments).