Mendelian disorders follow Mendel’s rules of inheritance. Which among the following is not an example of Mendelian disorder?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Klinefelter’s syndrome
Mendelian disorders come from a change or mutation in a single gene. They pass to the offspring by Mendel’s rules, and a pedigree can trace them. Chromosomal disorders come from the absence, excess or abnormal arrangement of whole chromosomes.
(1) Myotonic dystrophy — A Mendelian disorder. It is an autosomal dominant trait, controlled by one gene.
(2) Cystic fibrosis — A Mendelian disorder. It is a single-gene disorder.
(3) Colour blindness — A Mendelian disorder. It is a sex-linked recessive disorder, caused by a gene on the X chromosome.
(4) Klinefelter’s syndrome — Not a Mendelian disorder. It is a chromosomal disorder. The person has an extra X chromosome (XXY).
NCERT Extract:
Symbols Pedigree – …
