Which of the Following Is Not a Chromosomal Disorder?
Which of the Following Is Not a Chromosomal Disorder?
Question: Which of the following is not a chromosomal disorder?
Answer
What Are Chromosomal Disorders?
Chromosomal disorders result from abnormalities in the number or structure of chromosomes. They can occur because of changes such as an extra chromosome, a missing chromosome, or structural alterations in chromosomes.
Examples of Chromosomal Disorders
- Down syndrome: Caused by an additional copy of chromosome 21 (trisomy 21).
- Klinefelter syndrome: Characterised by an additional X chromosome, commonly represented as 47, XXY.
- Turner syndrome: Characterised by the absence of one X chromosome, commonly represented as 45, XO.
Why Is Haemophilia Not a Chromosomal Disorder?
Haemophilia is an X-linked recessive genetic disorder. It results from a mutation in a specific gene involved in blood clotting rather than from an abnormality in the number or structure of an entire chromosome.
Therefore, haemophilia is classified as a single-gene disorder, not a chromosomal disorder.
Chromosomal Disorders vs Single-Gene Disorders
| Chromosomal Disorders | Single-Gene Disorders |
|---|---|
| Involve chromosome number or structure | Usually involve mutation in a particular gene |
| Down syndrome | Haemophilia |
| Klinefelter syndrome | Sickle-cell anaemia |
| Turner syndrome | Phenylketonuria |
Frequently Asked Questions
Is haemophilia a chromosomal disorder?
No. Haemophilia is an X-linked recessive single-gene disorder.
What is an example of a chromosomal disorder?
Down syndrome, Klinefelter syndrome and Turner syndrome are important examples.
What causes Down syndrome?
Down syndrome is usually caused by the presence of an additional copy of chromosome 21.
Quick Revision
Chromosomal disorders → chromosome number/structure abnormality
Haemophilia → single-gene disorder → X-linked recessive
Conclusion
Among common genetic disorders, haemophilia is not a chromosomal disorder. It is a single-gene disorder caused by a mutation in an X-linked gene. In contrast, Down syndrome, Klinefelter syndrome and Turner syndrome are chromosomal disorders.
