Video Transcript
Which of the following is common between a person who has Klinefelter’s syndrome and
a person who has Turner’s syndrome? (A) The number of X chromosomes, (B) the presence of the X chromosome, (C) the
absence of the Y chromosome, or (D) having the same reproductive organs.
You may recall that the nucleus of a typical human body cell contains 46 chromosomes,
two of which are the sex chromosomes. These are the X and Y chromosomes, and the combination in which they are inherited
determines a person’s biological sex. If an individual has two X chromosomes, they are biologically female. And if they have one X chromosome and one Y chromosome, they are biologically
male.
Now let’s compare the two conditions this question is asking us about. Klinefelter’s syndrome only affects biological males, and it is characterized by
small, poorly functioning genitals and infertility. Individuals affected by Klinefelter’s syndrome have an additional copy of the X
chromosome, so they have two X chromosomes and one Y chromosome. Now let’s look at Turner’s syndrome. In contrast to Klinefelter’s, Turner’s syndrome only affects biological females, and
its main features are a short stature, impaired reproductive development, and
infertility. Turner’s syndrome is caused by a missing X chromosome, so affected individuals only
have one X chromosome rather than the usual two.
Now let’s return to our question. We’ve said that the two conditions are found in opposite biological sexes, which have
different reproductive organs, so we can eliminate answer option (D). We can also rule out answer option (C) because although the Y chromosome is absent in
Turner’s syndrome, it is present in Klinefelter’s syndrome. Finally, we can eliminate answer option (A) because a person with Klinefelter’s
syndrome has two X chromosomes, while a person with Turner’s syndrome only has
one.
We have therefore determined that the correct answer is (B). The common feature between a person with Klinefelter’s syndrome and a person with
Turner’s syndrome is the presence of the X chromosome.
