Chorionic villus sampling reveals a fetus has the karyotype 47, XXY. What is the diagnosis?
- Normal male
- Jacobs syndrome
- Edward syndrome
- Klinefelter syndrome
The chromosomal shorthand provides the total number of chromosomes in the individual, followed by the sex chromosomes for that individual. Additionally, chromosomal shorthand will indicate any chromosomal abnormality (like deletions or translocations).
In this question, we have an individual that has 47 chromosomes, 2 of which are X chromosomes and 1 of which is a Y chromosome. A normal male would have 46 chromosomes total, one of which would be an X chromosome and one of which would be a Y chromosome. Therefore we know that answer A is incorrect. Answer choice B is Jacobs syndrome. Jacobs syndrome occurs in males but these individuals have an extra Y chromosome. Therefore, the chromosomal shorthand of someone with Jacobs syndrome would be 47,XYY so this is not the correct answer. Edwards syndrome occurs when someone has an extra chromosome 18. The chromosomal shorthand for this would be 47,XX + 18 or 47, XY + 18, so answer choice C is incorrect. Answer choice D is Klinefelter syndrome. Individuals with Klinefelter syndrome have an extra X chromosome. Therefore the chromosomal shorthand for this syndrome is 47,XXY making D the correct answer.
