Read the paragraph and answer the question.
Broadly, genetic disorders may be grouped into two categories - Mendelian disorders and Chromosomal disorders. Mendelian disorders are mainly determined by alteration or mutation in the single gene. These disorders are transmitted to the offspring on the same lines as we have studied in the principle of inheritance. The trait may also be linked to the sex chromosome as in case of haemophilia. It is evident that this X-linked recessive trait shows transmission from carrier female to male progeny.
Which of the following disease is a result of aneuploidy ?
(A) Turner's Syndrome
(B) Klinefelter's Syndrome
(C) Down's Syndrome
(D) Phenylketonuria
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (B) and (C) only
Aneuploidy is the gain or loss of one or more chromosomes, caused by failure of the chromatids to separate during cell division.
(A) Turner's Syndrome — Correct. Loss of an X (45, X0).
(B) Klinefelter's Syndrome — Correct. Gain of an X (47, XXY).
(C) Down's Syndrome — Correct. Gain of chromosome 21.
(D) Phenylketonuria — Incorrect. It is a Mendelian disorder of one gene; the chromosome number is normal.
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 – “… Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called aneuploidy. For example, Down’s syndrome results in the gain of extra copy of chromosome 21. Similarly, Turner’s syndrome results due to loss of an X chromosome in human females.”