Write a note on Down’s syndrome.

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Write a note on Down’s syndrome.

Posted by Rajat Chauhan 5 years ago

CBSE > Class 12 > Biology

2 answers

Yogita Ingle 5 years ago

Down syndrome is a chromosomal disorder. It is due to aneuploidy of the autosome. There is one extra chromosome 21 or part of the chromosome present in all the cells or some cells.

The occurrence of Down syndrome is 1:800 live births. The major risk factor is the age of the mother. Most of the trisomy cases occur in the mother having age more than 35.

Down syndrome is caused due to abnormal cell division. During mitotic and meiotic cell division the chromosome pair separate so that each cell gets the copy of each chromosome. In down syndrome, the chromosomes are not able to separate, giving rise to cells with an unequal number of chromosomes. This phenomenon is called nondisjunction.

Nondisjunction happens, when chromosome segregates in anaphase before all of the replicated chromosomes’ kinetochores are attached to microtubules from opposite poles during metaphase. It results in one daughter cell having less chromosome and another with one extra chromosome.

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Anjali Kumawat 5 years ago

This disorder was first describe by LANGDON DOWN (1866). Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. Plam is broad with characteristics plam crease, physical, psychomotor and mental development is retarded.

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