Video Transcript
Klinefelter’s syndrome is an example of a syndrome caused by chromosomal abnormalities. How is Klinefelter’s syndrome caused? (A) Klinefelter’s syndrome is caused by the presence of an extra Y chromosome in cells. (B) Klinefelter’s syndrome is caused by structural changes in chromosome 21. (C) Klinefelter’s syndrome is caused by the presence of an extra X chromosome in cells. Or (D) Klinefelter’s syndrome is caused by the complete loss of an X chromosome.
This question asks us about the cause of Klinefelter’s syndrome, a common example of a condition caused by a chromosomal abnormality. So what exactly are chromosomal abnormalities? Humans generally have 46 chromosomes arranged into 23 pairs. The two chromosomes that make up the last pair are called the sex chromosomes, as these are the ones that determine our biological sex. If a person has two X chromosomes, they are said to be biologically female. If a person has one X and one Y chromosome, they are said to be biologically male.
Now coming back to the term chromosomal abnormalities, a chromosomal abnormality describes a change in the number or the structure of our chromosomes. This can lead to certain health problems, traits, or conditions.
Klinefelter’s syndrome, as we have mentioned, is an example of a condition caused by a chromosomal abnormality. This condition affects males who then experience low levels of testosterone and have difficulty producing healthy sperm. So how is this condition caused? Generally, biological males have one X chromosome and one Y chromosome. People with Klinefelter’s syndrome have one extra X chromosome. This means that instead of having the typical XY sex chromosomes, they have the combination XXY. Instead of having 46 chromosomes in total, they have 47.
With the information we now have, we can answer our question. The correct answer to what causes Klinefelter’s syndrome is answer choice (C). Klinefelter’s syndrome is caused by the presence of an extra X chromosome in cells.
