Which of the following are Mendelian disorders?
(A) Haemophilia
(B) Cystic fibrosis
(C) Sickle cell anaemia
(D) Down syndrome
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Only (A), (B) and (C)
Genetic disorders are of two broad kinds. Mendelian disorders are caused by a change (mutation) in a single gene, and they are inherited as Mendel’s laws predict. Chromosomal disorders are caused by the absence, excess or wrong arrangement of one or more whole chromosomes.
(A) Haemophilia — A Mendelian disorder. It is a sex-linked recessive disease in which a single protein of the blood-clotting chain is affected.
(B) Cystic fibrosis — A Mendelian disorder. It is caused by a mutation in a single gene.
(C) Sickle cell anaemia — A Mendelian disorder. It is an autosomal recessive trait caused by a single base change in the gene for the beta globin chain of haemoglobin.
(D) Down syndrome — Not a Mendelian disorder. It is a chromosomal disorder, caused by an extra copy of chromosome 21 (trisomy 21).
NCERT Extract:
Mendelian Disorders –
