Assertion :Polytene chromosomes have a high amount of DNA. Reason: Polytene chromosomes are formed by repeated replication.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

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Assertion is correct but Reason is incorrect.

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Both Assertion and Reason are incorrect.

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Solution

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
The absence of cell division after DNA replication which in turn causes multiplication of chromosome number of cells is called endo-reduplication. Polytene chromosomes in salivary glands of Drosophila are formed as a result of the endo-reduplication and the synapsis of homologs without cell division. Since chromosomes are the thread-like structures having DNA and associated proteins, multiplication of chromosome number also multiplies the DNA content. Therefore, polytene chromosomes carry a high amount of DNA. Thus, the correct answer is option A.

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