Principle-Of-Inheritance-And-Variation Question 614
Question: Based on Lyon’s hypothesis, what will be the number of Barr bodies found in a human female suffering from Down’s syndrome [AIEEE 2004]
Options:
A) 0
B) 1
C) 2
D) 3
Show Answer
Answer:
Correct Answer: B
Solution:
Down?s syndrome is a chromosomal abnormality in humans and is associated with an extra chromosome 21 (i.e.
chromosomal formula is 45 + xx = 47), while one of the two x-chromosomes becomes genetically inert and heteropycnotic and forms the Barr body.
Hence human female suffering from Down?s syndrome contains (2x - 1 = 1) one Barr body.
BETA
