Read the given passage and answer the question given below.
The sex linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny has been widely studied. In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected. Due to this in an affected individual a simple cut will result in non-stop bleeding. The heterozygous female (carrier) for the disease may transmit it to sons. The possibility of a female becoming a sufferer of disease is extremely rare because mother of such a female has to be at least carrier and the father should be sufferer. The family pedigree of Queen Victoria shows a number of suffering descendents as she was a carrier of the disease.
Identify the type of genetic disorder explained in this paragraph:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Mendelian Disorder
The passage describes a disease caused by a change in one gene (for one clotting protein) and passed on in a regular pattern, which makes it a Mendelian disorder.
Option (1) Pedigree Analysis — Incorrect. Pedigree analysis is the method of studying a trait through a family tree, not a type of disorder.
Option (2) Mendelian Disorder — Correct. Haemophilia is caused by alteration or mutation in a single gene and is passed on following the principles of inheritance, so it is a Mendelian disorder. It is sex-linked recessive.
Option (3) Chromosomal Disorder — Incorrect. Chromosomal disorders come from an extra, missing or abnormal chromosome.
Option (4) Incomplete dominance — Incorrect. Incomplete dominance is a pattern of inheritance, not a disorder.
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. 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.”