Most boys and men have two sex chromosomes. But what happens when a male has more than two sex chromosomes? In this lesson, we'll explore two examples of male aneuploidy: Klinefelter Syndrome and XYY Syndrome.
Christie is worried about her son, Zack. He is different from other teenage boys: he hasn't started puberty yet. He also has softer, more full breasts than boys usually do. He struggles in school and has been diagnosed with a learning disability. Christie is worried that something might be wrong.
Zack's differences might be caused by his genes. Usually, people have two sex chromosomes in their cells. For males, there is usually one X chromosome and one Y chromosome. But some people have additional chromosomes. Sex aneuploidy is a condition in which a person has more or less than two sex chromosomes. This can cause developmental issues, like those that Zack is displaying. Let's look closer at two examples of male aneuploidy: Klinefelter syndrome and XYY syndrome.
Remember Zack? He's a teenager, but hasn't started puberty. He has breasts that are more like girl's breasts than boys. In addition, he has a learning disability. Zack might have Klinefelter syndrome, which occurs when a male has one or more extra X chromosomes. As we mentioned before, most boys have one X and one Y chromosome, but boys with Klinefelter syndrome usually have two X chromosomes and one Y chromosome, though sometimes they can have three or more X chromosomes.
The symptoms of Klinefelter syndrome involve developmental delays. There might be delays in speech and language, and there might be learning disabilities, like Zack has. But there are also delays or struggles with physical development. The Y chromosome is in charge of male sexual development. But in Klinefelter syndrome, the extra X chromosome makes it hard for the Y chromosome to do its job.
As a result, boys with the syndrome often have less testosterone in their systems. Because testosterone is the hormone that is in charge of male physical development, Klinefelter syndrome often results in delayed or incomplete puberty. Some boys also develop breasts like females, like Zack has. Boys with Klinefelter syndrome might have less facial and body hair than other men, and they might end up being unable to have children.
Christie, Zack's mom, is worried that she might have done something to cause Zack's condition. But Zack's doctor reassures Christie that it's not her fault. Klinefelter syndrome is usually a result of a random event early during pregnancy, and there's nothing Christie could have done to cause it.
To help Zack deal with Klinefelter syndrome, his doctor suggests he meets with other boys who have sex aneuploidy. In his support group, Zack meets Charlie, who is both different and similar to Zack. Charlie is a lot taller than other boys his age, but unlike Zack, Charlie doesn't have any other physical abnormalities compared to other boys. But he does have a learning disability, like Zack, and some other developmental issues.
Charlie has XYY syndrome, which is a condition where a boy has an extra Y chromosome. In some ways, it is the opposite of Klinefelter syndrome: whereas Zack has an extra X chromosome, but a normal number of Y chromosomes, Charlie has an extra Y chromosome and a normal number of X chromosomes. But, like Klinefelter syndrome, XYY syndrome can cause developmental delays and learning disabilities. Like Zack, Charlie had delays in learning language and speaking when he was younger. He also took longer to learn to walk and control his body movements, which are motor development delays.
Other boys with XYY syndrome might have weak muscles or tics, in which they move involuntarily. Some also display behavioral or emotional difficulties. But the symptoms of XYY syndrome vary widely, and someone could have it and display little or no symptoms of it at all. Like Klinefelter syndrome, XYY syndrome is usually caused by a random event and is not inherited or the result of any behavior on the part of the mother.
Sex aneuploidy occurs when a person has more or less than the normal two sex chromosomes. Males normally have one X and one Y chromosome. However, Klinefelter syndrome involves having two or more X chromosomes and one Y chromosome. This results in a lower than normal amount of testosterone, which can lead to delays in physical development, the development of female breasts, learning disabilities, and speech and language delays.
Meanwhile, XYY syndrome occurs when a boy has one X chromosome, but two Y chromosomes. These boys are often taller than average, but display few other physical symptoms. However, it can cause developmental delays and learning disabilities, including speech and language delays, motor development delays, weak muscles or tics, and behavioral or emotional difficulties. Both Klinefelter syndrome and XYY syndrome are a result of a random event in utero.
Following this video lesson, you will be able to:
- Define sex aneuploidy
- Describe the causes and symptoms of Klinefelter syndrome and XYY syndrome