(D) Down's syndrome is a chromosomal disorder caused by the presence of an extra copy of chromosome number $21$ (trisomy of $21$).In a normal human ce

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(D) Down's syndrome is a chromosomal disorder caused by the presence of an extra copy of chromosome number $21$ (trisomy of $21$).In a normal human cell,there are $46$ chromosomes ($23$ pairs).Due to the presence of an additional chromosome $21$,the total number of chromosomes in an individual with Down's syndrome becomes $46 + 1 = 47$.Therefore,the correct option is $47$.

Class 12 Biology Principles of Inheritance and Variation Chromosomal disorders

Medium

In Down's syndrome $(Mongolism)$,each cell has how many chromosomes?

A
$21^{st}$ pair having one less
B
$23^{rd}$ pair with one less
C
$45$
D
$47$

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Chapter

Principles of Inheritance and Variation

Subtopic

Chromosomal disorders

In a diploid set of chromosomes,the deletion or addition of a chromosome leads to:

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What is the cause of $Down's$ syndrome?

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Match Column $I$ with Column $II$ and find the correct answer.
Column $I$ Column $II$
$(A)$ Aneuploidy $(i)$ Increase in whole set of chromosomes
$(B)$ Monoploidy $(ii)$ Loss or gain of a chromosome
$(C)$ Polyploidy $(iii)$ Two sets of chromosomes
$(D)$ Diploidy $(iv)$ $A$ single set of chromosomes

Column $I$	Column $II$
$(A)$ Aneuploidy	$(i)$ Increase in whole set of chromosomes
$(B)$ Monoploidy	$(ii)$ Loss or gain of a chromosome
$(C)$ Polyploidy	$(iii)$ Two sets of chromosomes
$(D)$ Diploidy	$(iv)$ $A$ single set of chromosomes

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