Question Video: Identifying Turner Syndrome from a Karyotype | Nagwa Question Video: Identifying Turner Syndrome from a Karyotype | Nagwa

Question Video: Identifying Turner Syndrome from a Karyotype Biology • First Year of Secondary School

Karyotypes are images of a person’s chromosomes that can be used to determine chromosomal abnormalities. Which syndrome is likely to be caused by the chromosomal abnormality shown in the karyotype provided? [A] Klinefelter syndrome [B] Turner syndrome [C] Down syndrome

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Video Transcript

Karyotypes are images of a person’s chromosomes that can be used to determine chromosomal abnormalities. Which syndrome is likely to be caused by the chromosomal abnormality shown in the karyotype provided? (A) Klinefelter syndrome, (B) Turner syndrome, or (C) Down syndrome.

Karyotypes, like the one shown here, depict all the chromosomes found in a particular cell of a person. In a typical body cell, we would expect to see 46 chromosomes, arranged in 23 pairs. 22 of these pairs are autosomes, which means they have nothing to do with determining biological sex. The final pair are the sex chromosomes, X and Y, which are responsible for determining whether a person is biologically male or female. If someone has two X chromosomes, they are biologically female. And if they have one X chromosome and one Y chromosome, they are biologically male. In a sex cell, which is also known as a gamete, we would expect to see just 23 chromosomes.

Now let’s look at the three syndromes given in the question and see how each one would affect the typical karyotype. Klinefelter syndrome is a condition which only affects biological males. It’s caused by an individual having an additional X chromosome. In other words, they have two X chromosomes and one Y chromosome. The main features of Klinefelter syndrome are having small, poorly functioning genitals and being infertile.

By contrast, Turner syndrome only affects biological females. It’s caused by an individual only having one normal X chromosome, rather than the usual two. Turner syndrome is characterized by having a short stature, impaired reproductive development, and being infertile.

Finally, Down syndrome is caused by the presence of an extra copy of chromosome 21. This means affected individuals have three copies of chromosome 21, rather than the usual two. Because Down syndrome does not involve a change to the sex chromosomes, it can affect both biological males and females. The main features of Down syndrome are impaired growth, intellectual disability, and characteristic facial features.

If we now return to the karyotype provided in the question, we can see that this individual only possesses one copy of the X chromosome. We can therefore deduce that the correct answer is (B). The chromosomal abnormality shown in the karyotype provided is likely to cause Turner syndrome.

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