Q81 / 200 · MHT CET - Medical 2026 (25 April Shift 2) · Biology
Extra copy of 21st chromosome causes _________ in human.
- ATurner's syndrome
- BKlinefelter's syndrome
- CThalassemia
- Correct answerDDown's syndrome
Solution
Down's syndrome is a genetic disorder caused by the presence of an additional copy of chromosome $21$, also known as Trisomy $21$.
Turner's syndrome is caused by the absence of one of the X chromosomes, resulting in a $45$, X$0$ karyotype.
Klinefelter's syndrome is caused by the presence of an additional X chromosome, resulting in a $47$, XXY karyotype.
Thalassemia is an autosomal recessive blood disorder.
Therefore, an extra copy of the $21$st chromosome causes Down's syndrome.
Answer: Down's syndrome
Turner's syndrome is caused by the absence of one of the X chromosomes, resulting in a $45$, X$0$ karyotype.
Klinefelter's syndrome is caused by the presence of an additional X chromosome, resulting in a $47$, XXY karyotype.
Thalassemia is an autosomal recessive blood disorder.
Therefore, an extra copy of the $21$st chromosome causes Down's syndrome.
Answer: Down's syndrome
Hence, the correct answer is option: 'D'.