The cause of Down’s syndrome is

Correct option is B

Down’s syndrome is caused by Trisomy 21, which is the presence of an extra copy of chromosome 21. This chromosomal abnormality occurs due to nondisjunction during cell division, leading to an embryo with three copies of chromosome 21 instead of the usual two. Down's syndrome is characterized by distinctive facial features, developmental delays, intellectual disabilities, and an increased risk of certain medical conditions such as congenital heart defects and thyroid disorders. It is one of the most common genetic disorders caused by chromosomal abnormalities.

Information Booster

1. Down’s syndrome is named after Dr. John Langdon Down, who first described it in 1866.
2. The risk of having a child with Down’s syndrome increases with maternal age, particularly for mothers over the age of 35.
3. The syndrome is associated with physical traits like a flat facial profile, almond-shaped eyes, and a single deep crease across the palm (simian crease).
4. Early intervention programs, including speech and occupational therapies, can significantly improve quality of life.
5. The average life expectancy for individuals with Down’s syndrome has increased significantly with better healthcare.
6. Diagnostic techniques include prenatal tests like amniocentesis and chorionic villus sampling (CVS).

Additional Knowledge

(A) Trisomy – 20: This is a very rare chromosomal condition and not associated with Down’s syndrome. It may result in developmental abnormalities, but it is unrelated to Trisomy 21.

(C) XXY chromosome: This refers to Klinefelter syndrome, a condition affecting males where they have an extra X chromosome. It causes symptoms such as reduced testosterone levels, infertility, and learning difficulties, but it is unrelated to Down’s syndrome.

(D) Trisomy – 22: This rare chromosomal disorder is associated with severe developmental and physical abnormalities. It is not linked to Down’s syndrome but may result in pregnancy loss or other serious complications.