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4.Principles of Inheritance and Variation
normal
In Barr body (sex-chromatin) of a normal female
A
One of the $X$-chromosome of paternal side becomes inactive to form Barr body
B
$Y$-chromosomes form Barr body
C
Heterochromatin condense near centre of nucleus to form Barr body
D
One of the $X$-chromosome of maternal side becomes inactive and form Barr body near nuclear membrane
Solution
In body cells of a normal female, one of the $X$-chromosome become inactive and form Barr body near the nuclear membrane.
$XY$ genotype has no Barr body.
$XX$ genotype has single Barr body.
$XXX$ genotype have two Barr bodies.
$XXXX$ genotype have three Barr bodies.
Standard 12
Biology
