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 is not a Mendelian disorder ?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Turner's Syndrome
Option (1) Cystic Fibrosis — A Mendelian disorder. Autosomal recessive.
Option (2) Turner's Syndrome — Not a Mendelian disorder. It is a chromosomal disorder: one X chromosome is missing.
Option (3) Sickle cell anaemia — A Mendelian disorder. Autosomal recessive.
Option (4) Thalassaemia — A Mendelian disorder. Autosomal recessive.
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:
Mendelian Disorders – “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. … Most common and prevalent Mendelian disorders are Haemophilia, Cystic fibrosis, Sickle-cell anaemia, Colour blindness, Phenylketonuria, Thalassemia, etc.”
Chromosomal Disorders – “The chromosomal disorders on the other hand are caused due to absence or excess or abnormal arrangement of one or more chromosomes. … 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.”