Read the following passage carefully and answer the given questions.
Mendelian 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 pattern of inheritance of such Mendelian disorders can be traced in a family by the pedigree analysis. Most common and prevalent Mendelian disorders are Haemophilia, Cystic fibrosis, Sickle cell anaemia, Colour blindness, Phenylketonuria, Thalassemia, etc. It is important to mention here that such Mendelian disorders may be dominant or recessive. By pedigree analysis one can easily understand whether the trait in question is dominant or recessive. Similarly, 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 one of the following is an autosomal dominant Mendelian disorder?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Myotonic dystrophy
A Mendelian disorder is autosomal dominant when its gene is on an autosome (not on a sex chromosome) and one copy of the altered gene is enough to show the disorder.
(1) Sickle-cell anaemia — Incorrect. It is autosomal recessive. It shows only when both alleles are altered (HbSHbS).
(2) Myotonic dystrophy — Correct. It is the example of an autosomal dominant trait in pedigree analysis.
(3) Colour blindness — Incorrect. It is a sex-linked (X-linked) recessive disorder.
(4) Haemophilia — Incorrect. It is also a sex-linked recessive disorder, as the passage says.
Note 1: This passage is taken from NCERT as it is. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
Note 2: A similar question was also asked in CUET (UG) 2026 on 20-05-2026 (Slot 1) and on 19-05-2026 (Slot 1).
NCERT Extract:
Mendelian 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 pattern of inheritance of such Mendelian disorders can be traced in a family by the pedigree analysis. Most common and prevalent Mendelian disorders are Haemophilia, Cystic fibrosis, Sicklecell anaemia, Colour blindness, Phenylketonuria, Thalassemia, etc. It is important to mention here that such Mendelian disorders may be dominant or recessive.”
