Read the given paragraph and answer the question:
Humans have 23 pairs of chromosomes. 22 pairs are exactly same in both males and females; these are the autosomes. A pair of X-chromosome are present in the female, whereas the presence of an X and Y chromosome are determinant of the male characteristic.
A number of disorders in human beings have been found to be associated with the inheritance of changed or altered genes or chromosomes. Broadly, genetic disorder may be grouped into two categories – Mendelian disorders and Chromosomal disorders.
A disorder caused due to absence of one of the 'X' chromosome is -
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Turner's Syndrome
Option (1) Turner's Syndrome — Correct. Turner’s syndrome is caused by the absence of one X chromosome: 44 + XO, a total of 45. Such females are sterile, as the ovaries are rudimentary, and lack other secondary sexual characters.
Option (2) Down's Syndrome — Incorrect. Down's syndrome is caused by an extra copy of chromosome 21 (trisomy 21), an autosome. Nothing is missing.
Option (3) Klinefelter's Syndrome — Incorrect. Klinefelter's syndrome is the opposite case: an extra X chromosome in a male (44 + XXY).
Option (4) Thalassemia — Incorrect. Thalassemia is a Mendelian disorder of the globin genes, not a change in chromosome number.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Chromosomal Disorders – “… 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).”
