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Q.
Karyotype of Down’s syndrome has how many
chromosomes?
Principles of Inheritance and Variation
Solution:
Karyotype of people suffering from Down’s
syndrome have $47$ chromosomes ( $45 + XY$ in males,
$45 + XX$ in females) instead of $46$. It is caused due to
the presence of an extra chromosome, i.e. chromosome
number $21$. Thus, it is also known as $21$ trisomy.