Choose the incorrect statements from the following:
A. Klinefelter's syndrome is caused due to the presence of an additional copy of X-chromosome, resulting into a karyotype of 47, XXY.
B. An individual with Klinefelter's syndrome shows gynaecomastia, and such individuals are fertile.
C. Turner's syndrome is caused due to the absence of one of the X chromosomes, i.e., 45 with X0.
D. A female with Turner's syndrome shows tall stature with feminised character.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → B and D only
Klinefelter’s syndrome and Turner’s syndrome are chromosomal disorders caused by a change in the number of sex chromosomes. Klinefelter’s syndrome has one X too many (XXY). Turner’s syndrome has one X too few (X0). The question asks for the incorrect statements.
A. Klinefelter's syndrome is caused due to the presence of an additional copy of X-chromosome, resulting into a karyotype of 47, XXY. — True. An extra X-chromosome added to the normal 46, XY gives a karyotype of 47, XXY.
B. An individual with Klinefelter's syndrome shows gynaecomastia, and such individuals are fertile. — False. The first part is right: gynaecomastia (development of breast) is expressed along with masculine development. But such individuals are sterile, not fertile.
C. Turner's syndrome is caused due to the absence of one of the X chromosomes, i.e., 45 with X0. — True. One of the two X chromosomes is absent, so the karyotype is 45 with X0.
D. A female with Turner's syndrome shows tall stature with feminised character. — False. “Tall stature with feminised character” is the label for Klinefelter’s syndrome in Figure 4.17 (a). A female with Turner’s syndrome shows short stature and underdeveloped feminine character, Figure 4.17 (b).
Note: Statement D did not come from any paragraph. It was sitting quietly under a drawing as a three-word label. Labels look like decoration, but examiners read them as text, so give the small print under every figure a proper look.
NCERT Extract:
Chromosomal Disorders – “Klinefelter’s Syndrome : This genetic disorder is also caused due to the presence of an additional copy of X-chromosome resulting into a karyotype of 47, XXY. Such an individual has overall masculine development, however, the feminine development (development of breast, i.e., Gynaecomastia) is also expressed (Figure 4.17 a). Such individuals are sterile. Turner’s Syndrome : Such a disorder is caused due to the absence of one of the X chromosomes, i.e., 45 with X0, Such females are sterile as ovaries are rudimentary besides other features including lack of other secondary sexual characters (Figure 4.17 b).”
Figure 4.17 Diagrammatic representation of genetic disorders due to sex chromosome composition in humans : (a) Klinefelter Syndrome; (b) Turner’s Syndrome