Question

A person with 44A + XXY chromosome setup has gynecomastia and is barr body positive. They have symptoms of
A) Turner’s syndrome
B) Klinefelter’s syndrome
C) Down’s syndrome
D) Edward’s syndrome

Answer 1

Hint: These are characterized by trisomy of sex chromosome. They are male individuals having very low sperm count and therefore, they are sterile.

Complete Answer:
- In human beings, trisomics (2n = 47) and monosomics (2n = 45) are well known. Trisomy or monosomy may involve a sex chromosome or an autosome. Turner’s syndrome and Klinefelter’s syndrome are the examples of aneuploidy involving sex chromosomes. Down’s syndrome and Edward’s syndrome are examples of autosomal aneuploidy.

1) Turner's syndrome is characterized by monosomy of X-chromosome. It is represented as 44 +XO. The individuals with the syndrome are sterile females with webbed necks. They lack a barr body as they have only one X-chromosome.
2) Klinefelter’s Syndrome is characterized by a trisomy of the X-chromosome. It is marked by the presence of one or more extra X chromosomes in the individual (44+XXY/ 44+XXXY/ 44+XXXXY). A person with Klinefelter’s syndrome can have one or more barr bodies, depending on the number of X-chromosome. The individuals having this syndrome are sterile males with small poorly functioning testicles and gynecomastia (enlarged breasts).
3) Down's syndrome is also known as trisomy 21 because it is caused due to trisomy of chromosome 21. It is represented as 45 +XY or 45+XX. Patients with Down syndrome are short in stature. They are characterized as low in mentality but they can be trained in routine mechanical skills.
4) Edward's syndrome is caused due to trisomy of chromosome 18 that leads to severe physical birth defects in infants.

- Down's syndrome and Edward's syndrome are caused due to defects in autosomes and they do not exert any effect on sexual characters. Individuals with Turner’s syndrome do not have a barr body.

Therefore, the correct answer is B, i.e., Klinefelter’s Syndrome.

Note:
- In humans the homogametic sex (X X) is female and heterogametic sex (XY) is male. To compensate the dosage of X-linked genes in human male and females, one X-chromosome in females gets characteristically condensed and inactivated.
- It is present as a dark stained body near the nuclear envelope and is termed as a barr body. The number of barr bodies is always one less than the total number of X chromosomes present in the individual.