Turner Syndrome and Trisomy X: Types of Sex Chromosome Aneuploidy

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  • 0:04 Aneuploidy
  • 1:11 Turner Syndrome
  • 3:18 Trisomy X
  • 5:46 Lesson Summary
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Lesson Transcript
Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

Most females have two X chromosomes, which is what makes them women. But what happens when there are more or less than two X chromosomes in a woman's DNA? In this lesson, we'll explore Turner syndrome and Trisomy X.


Jennie is a happy little girl, but she has some issues. She's very short for her age, and her neck is very wide. Her IQ is normal for her age, but she struggles with understanding things in school, and also doesn't understand other people and their feelings and motivations.

Jennie's friend Carrie has some similar problems. She, too, has a normal IQ, though hers is lower than her brothers and sister, and she also struggles in school. She's very shy and introverted, and feels awkward around others. But Carrie is also different from Jennie. She's very tall, where Jennie is very short.

What's going on with Jennie and Carrie? They might have a type of sex chromosome aneuploidy, where the number of sex chromosomes in a cell is not the normal number. For example, girls normally have two X chromosomes in each cell, but some people have more or less than that. Let's look at two genetic disorders involving sex chromosome aneuploidy in girls: Turner syndrome and trisomy X.

Turner Syndrome

Remember Jennie? She's short for her age and has trouble in school. She also looks a little different from other girls: she's got a very wide neck and her fingers and toes are unusually short.

Turner syndrome is a genetic disorder that affects females. It occurs when one of the sex chromosomes is missing or partially missing. Remember that girls normally have two X chromosomes, but in Jennie and other girls with Turner syndrome, there's only one X chromosome.

What does this mean? Well, this can explain some of what makes Jennie different from her peers. Physical symptoms of Turner syndrome include short stature, wide neck, unusually short fingers and toes, small jaw, fertility issues, and arms that turn outward at the elbows, among others. So the fact that Jennie is very short, has a wide neck, and short fingers and toes, could be explained by Turner syndrome.

The physical symptoms are not the only ones, though. Remember that Jennie struggles in school, despite having a normal IQ. She also has trouble understanding others. Psychological symptoms of Turner syndrome include learning disabilities and difficulty in reading others' emotional states.

Jennie's mom feels guilty and wonders if she did something to cause Jennie's Turner syndrome. Is she to blame? No. Turner syndrome appears to be a random occurrence and not due to environmental factors or part of a family's history.

Turner syndrome is essentially a genetic disorder that affects development. This could mean that it inhibits Jennie's ability to develop physically (causing her to be short or infertile or to have issues with heart or immune system functions) and her ability to develop psychologically (causing her to have a learning disability or social issues).

What can Jennie and her parents do? A doctor can create a treatment plan for Jennie. It will most likely include growth hormone therapy and estrogen to help her grow physically and go through puberty. The doctor may also suggest other treatments to help with some of her other symptoms.

Trisomy X

Jennie's not the only one struggling. Remember Carrie? Unlike Jennie, she doesn't have a problem with growth; in fact, she's grown too much and now she's very tall for her age! But, like Jennie, she struggles some with school. Her IQ is normal, but lower than her siblings' IQs, and she's very introverted.

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