Question

Trisomy of 18\textsuperscript{th} chromosome causes

• A. Turner's syndrome
• B. Down syndrome
• C. Klinefelter's syndrome
• D. Edwards syndrome

Hint:

Trisomy 21 → Down syndrome
Trisomy 18 → Edwards syndrome
Trisomy 13 → Patau syndrome

Answer 1

The Correct Option is D

Trisomy refers to the presence of an extra chromosome in a pair. In the case of Edwards syndrome, there is an extra copy of chromosome 18 (i.e., trisomy 18). It is a genetic disorder that leads to severe developmental and physical abnormalities and is often fatal within the first year of life.
- Turner's syndrome is caused by the presence of a single X chromosome (monosomy XO) in females.
- Down syndrome is caused by trisomy of chromosome 21.
- Klinefelter's syndrome results from an additional X chromosome in males (XXY). Hence, trisomy 18 leads to Edwards syndrome, making option (4) the correct answer.

Answer 2

Trisomy of the 18th chromosome occurs when there is an extra copy of chromosome 18 in the cells of the body instead of the usual two copies. This chromosomal abnormality leads to a genetic disorder called Edwards syndrome. The presence of this extra chromosome disrupts the normal course of embryonic and fetal development, resulting in severe physical and intellectual disabilities.

Individuals affected by Edwards syndrome exhibit a wide range of symptoms including low birth weight, a small head (microcephaly), a small jaw (micrognathia), and characteristic clenched fists with overlapping fingers. Other common features include congenital heart defects, abnormalities of the kidneys and other organs, feeding difficulties, and severe developmental delays. Many infants with this condition have a significantly shortened lifespan, with a high risk of mortality within the first year of life due to complications such as heart failure or respiratory problems.

Edwards syndrome demonstrates the critical role of proper chromosomal number and structure in human development. The extra genetic material in chromosome 18 disrupts normal gene expression, leading to the complex clinical manifestations observed. Prenatal screening and genetic counseling are important for early detection and management of the condition.

In summary, trisomy of the 18th chromosome causes Edwards syndrome, a severe genetic disorder characterized by multiple congenital abnormalities and high infant mortality.